Claims:1. A sheet processing apparatus comprising:
a support member that supports a sheet, a through part being formed in the support member;
a transmitting unit that transmits ultrasonic waves from a transmitting surface;
a reflecting unit that reflects the ultrasonic waves transmitted from the transmitting unit and passed through the through part; and
a receiving unit that receives on a receiving surface the ultrasonic waves reflected by the reflecting unit,
wherein
the receiving surface faces downward, and the transmitting surface is parallel to a vertical direction or faces downward, or
the transmitting surface faces downward, and the receiving surface is parallel to a vertical direction or faces downward.

2. The sheet processing apparatus as claimed in claim 1, further comprising
a storing unit that stores the sheet therein,
wherein the support member is arranged in the storing unit.

3. The sheet processing apparatus as claimed in claim 2, wherein
one of the transmitting unit and the receiving unit is arranged in one space separated by the support member from the other space and
the other of the transmitting unit and the receiving unit is arranged in the other space.

4. The sheet processing apparatus as claimed in claim 2, wherein both the transmitting unit and the receiving unit is arranged in one space separated by the support member from the other space inside the storing unit.

5. The sheet processing apparatus as claimed in claim 4, wherein the transmitting unit and the receiving unit are formed integrally.

6. The sheet processing apparatus as claimed in any one of claims 2 to 5, wherein
the storing unit is a stacker formed integrally with the sheet processing apparatus, or
the storing unit is a container detachably attached to the sheet processing apparatus.

7. The sheet processing apparatus as claimed in any one of claims 2 to 6, further comprising
a stacking wheel that receives the sheet sent into the storing unit and stacks the sheet on the support member,
wherein the stacking wheel is arranged at a position where the ultrasonic waves transmitted and received between the transmitting unit and the receiving unit strike against the stacking wheel.

8. The sheet processing apparatus as claimed in any one of claims 2 to 7, wherein the support member is configured to move depending on the number of sheets stacked on the support member.

9. The sheet processing apparatus as claimed in any one of claims 2 to 8, wherein the through part is a cutout portion formed in the support member.

10. The sheet processing apparatus as claimed in claim 1, further comprising
a transport path that transports the sheet,
wherein the support member is a bottom part of the transport path, and
the support member supports the sheet being transported.

11. The sheet processing apparatus as claimed in claim 10, wherein
one of the transmitting unit and the receiving unit is arranged in one space separated by the support member from the other space and
the other of the transmitting unit and the receiving unit is arranged in the other space.

12. The sheet processing apparatus as claimed in claim 10, wherein both the transmitting unit and the receiving unit is arranged in one space separated by the support member from the other space.

13. The sheet processing apparatus as claimed in claim 12, wherein the transmitting unit and the receiving unit are formed integrally.

14. The sheet processing apparatus as claimed in any one of claims 1 to 13, wherein the ultrasonic waves pass through the through part in the vertical direction.

15. The paper sheet detection apparatus as claimed in any one of claims 1 to 13, wherein the ultrasonic waves pass through the through part in a direction inclined at a predetermined angle with regard to the vertical direction.
, Description:AS ATTACHED