1. A three-dimensional deposition device which forms a
three-dimensional object by depositing a formed layer on a
base unit, comprising:
a powder supply unit which supplies a powder material;
a light irradiation unit which irradiates the powder material with a light beam and sinters or melts and solidifies at least a part of the powder material irradiated with the light beam to form the formed layer;
a three-dimensional deposition chamber which is sealed from an outside and accommodates the powder supply unit, the light irradiation unit, and the base unit therein;
a gas discharge unit which discharges a gas inside the three-dimensional deposition chamber; and
a gas introduction unit which introduces a predetermined gas into the three-dimensional deposition chamber,
wherein a predetermined gas atmosphere is formed inside the three-dimensional deposition chamber when the gas discharge unit discharges a gas inside the three-dimensional deposition chamber and the gas introduction unit introduces the predetermined gas into the three-dimensional deposition chamber.
2. The three-dimensional deposition device according to
claim 1,
wherein the powder supply unit injects the powder material from an opening of a front end thereof toward the base unit,
the light irradiation unit irradiates the powder material feeding from the powder supply unit toward the base unit with the light beam from the opening of the front end thereof so that the powder material is melted and the

melted powder material is solidified on the base unit, and the three-dimensional deposition chamber accommodates the opening of the powder supply unit and the opening of the light irradiation unit.
3. The three-dimensional deposition device according to
claim 2,
wherein the powder supply unit is concentrically disposed on an outer periphery of the light irradiation unit, the powder supply unit and the light irradiation unit forms a deposition unit which includes an inner tube surrounding a path causing the light beam of the light irradiation unit to pass therethrough and an outer tube covering the inner tube and forming a powder passage causing the powder material to flow therethrough between the inner tube and the outer tube, and the deposition unit is movable in one direction, and
the three-dimensional deposition device includes a telescopic unit which is attached to the deposition unit and expands and contracts in the one direction while sealing the three-dimensional deposition chamber from the outside, in accordance with the movement of the deposition unit.
4. The three-dimensional deposition device according to
claim 3,
wherein the deposition unit is movable only in one axis direction.
5. The three-dimensional deposition device according to
any one of claims 2 to 4, comprising:
a cover unit which is attached to the powder supply unit and the light irradiation unit and covers a part in

which the formed layer of the base unit is formed;
a cover gas discharge unit which discharges a gas inside the cover unit; and
a cover gas introduction unit which introduces a predetermined gas into the cover unit,
wherein when the cover gas discharge unit discharges a gas inside the cover unit and the cover gas introduction unit introduces the predetermined gas thereinto, the cover unit forms the predetermined gas atmosphere in the periphery of the base unit.
6. The three-dimensional deposition device according to any one of claims 1 to 5, comprising:
a spare chamber which connects the three-dimensional deposition chamber to the outside of the three-dimensional deposition chamber and is sealed from the three-dimensional deposition chamber and the outside of the three-dimensional deposition chamber,
wherein the base unit is moved from the outside of the three-dimensional deposition chamber into the three-dimensional deposition chamber through the spare chamber so that the base unit is accommodated in the three-dimensional deposition chamber.