Provided is a method of removing a cartridge, that is to be removed, that is housed in a deep side of a cell and stuck on a wall surface of the cell without increasing the number of components. In order to remove the cartridge stuck on the wall surface of the cell, the method includes a pressing step and a releasing step. In the pressing step, a picker mechanism is abutted on a latch lever, and then moved so as to move the latch lever from an engaged position to a released position. This presses the latch lever to increase the urging force of the urging unit. In the releasing step, after the pressing step, the picker mechanism is moved away from the cell to release the urging force of the latch lever spring.