To easily mount a pressure regulating device on a pressure regulating object.

The pressure regulating device 10 includes a pressurization chamber 12, a discharge chamber 13 connected to a tire inside I through a non-return valve 13rsv, a pressurization piston 16 for pressurizing air introduced into the pressurization chamber 12, a piezoelectric actuator 14 deformed by voltage application to drive the pressurization piston 16, and a booster piston 15 for boosting air in the discharge chamber 13. The booster piston 15 is prepared separately from the pressurization piston 16. A cross section at the pressurization chamber 12 side of the booster piston 15 is smaller than a cross section of the pressurization chamber 12, and a cross section at the discharge chamber 13 side of the booster piston 15 is not larger than the cross section at the pressurization chamber 12 side of the booster piston 15.