A detachable body includes: a detachable body main body that is to be attached to an attachment/detachment subject apparatus in a detachable manner, the detachable main body having an internal space and a connection hole which connects the internal space and an external space; and an opening/closing member that is attached to the detachable body main body, the opening/closing member being movable between an opening position where the connection hole is exposed and a closing position where the connection hole is closed. The opening/closing member includes: an opening/closing member main body that is curved parallel with a movement direction of the opening/closing member between the opening position and the closing position; and a plane portion that has a flat surface, the plane portion being formed in an outer surface of the opening/closing member main body.