The device for inflating pneumatic tires comprises an inlet of pressurized air and an outlet for sending the air into a pneumatic tire. A first circuit of the device is divided into an initial tract and a final tract, which connects the inlet with the outlet, passing through a first on-off valve provided with a membrane. A second circuit of the device connects the inlet with a first chamber of the first on-off valve. The first chamber is also connected to a pressure regulator connected at outlet to a second on-off valve, which intercepts the air flow. A third circuit connects the outlet to a first chamber of the second on-off valve.