To execute the calibrating work of a pressure apparatus in a short time even where there is no power source such as an alternating current power supply, by arranging a power supply which drives a compressor and can accumulate electricity.

A storage battery 10 is switched to a compressor 1 side or a charger connecting terminal 13 side through a pressurizing/charging switch 11. At the time of calibrating, the switch 11 is connected to a pressurizing side, the air compressor 1 is operated, and compressed air is outputted. When this compressed air is supplied to the primary side of a pressure intensifying valve 2, secondary side pressure is also gradually increased by pressure intensifying action. This pressure is made to serve as external output as it is, and apply pressure to a target apparatus to be calibrated. During the normal calibrating work of the pressure apparatus, pressurizing is interrupted around a target pressure while watching the indication of a pressure gauge 4, fine set is matched to the target pressure while rotating the knob of a pressure fine regulating cylinder 5 and watching the indication of a digital pressure gauge.