To accurately treat failure where a valve element of a differential pressure valve of an electric automobile is stuck.

A differential pressure valve 9 which decompresses input hydraulic pressure Pin transmitted from a master cylinder to an input port 21 and transmits the decompressed output hydraulic pressure Pout from an output port 22 to a brake cylinder is equipped with a valve element 30 energized in the seating direction to a valve seat 252 with thrust fs generated by a linear solenoid 31. When the valve element 30 is fixed in the seating condition to the valve seat 252 and hydraulic pressure of the input port 21 is not transmitted to the output port 22, a differential pressure piston 43 provided for a communication passage 42 for connecting the input port 21 with the output port 22 moves up against a return spring 45 due to the differential pressure between the input port 21 and the output port 22, and therefore a differential pressure driven switch S3 turns on to alarm a driver.