A pressure source for a pressure device has a pump for pumping fluid from a tank, an accumulator connected to the pump and to a pressure device, a device for detecting the pressure in the accumulator, and a control system for controlling the operation of the pump in an ON/OFF manner based on results of detection of the pressure detecting device. The pressure detecting device includes a pressure switch to detect pressure in the accumulator to produce an ON/OFF signal, and a pressure sensor outputting a pressure signal corresponding to pressure in the accumulator. The control system judges whether the pressure sensor is normal or out of order, and when the pressure is normal, controls the operation of the pump with the pressure signal. The pressure signal and the ON/OFF signal are compared with each other, and when these signals do not correspond, the pressure switch is determined to be out of order, and when the pressure sensor is out of order, the pump operation is controlled with the ON/OFF signal. In this way, the pump can be controlled appropriately, irrespective of any trouble or abnormality in the detecting device.