A printing apparatus adapted to have a cartridge detachably mounted thereon includes a cartridge mounting structure, a printing material supply tube, a plurality of apparatus-side terminals and a lever used for attachment and detachment of the cartridge to and from the printing apparatus. The lever has an operating member, a first apparatus-side locking portion and an axis of rotation. When an external force is applied to the operating member of the lever from the +X-axis direction to the −X-axis direction, the lever moves the first apparatus-side locking portion about the axis of rotation from a specified locking position toward the +X-axis direction and disengages the first apparatus-side locking portion from a first cartridge-side restriction portion, so as to eliminate the restriction of motion of the cartridge. This ensures stable electrical connection between cartridge-side terminals and apparatus-side terminals.