To solve problems with a seal provided at an inner circumference of a powder supply port, wherein the seal comes in contact with an outer circumference of a delivery port and scratched, resulting in damage or impairing sealability when the delivery port of a powder container is put in and out the powder supply port, and wherein powder is scattered and powder dust is generated due to "inversion flipping" and restoring vibration from a bent state to a flat plate when drawing the delivery port.

A seal 2 of a powder supply port 8 provided between the powder supply port and an outer circumference of an inserted delivery port 6 is annularly installed at an inner circumference of the powder supply port 8. The section is formed so as to be capable of expanding and contracting. The seal abuts against the outer circumference of the inserted delivery port 6 in the expanding state, and forms a gap between the seal and the outer circumference in the contracting state.