In a printing apparatus of an off-carriage type, when a pump motor is rotated regularly for delivering pressurizing air to an ink cartridge, rotation thereof is converted into a linear reciprocating movement of a pressing member by a cam mechanism and a pressurizing operation is executed by repeating to operate to expand and contract a diaphragm. On the other hand, the pump motor is started to rotate inversely, a driven part is rotated by a friction clutch mechanism, and a pressing portion of the driven part is brought into contact with a valve opening lever of an atmospheric release valve. At this occasion, the valve opening lever is pivoted to bring a valve hole into an opened state and pressurizing air is discharged to outside by bringing the atmospheric release valve into an opened state.