To provide a piston advancing limit alarming device of a disc brake device capable of detecting advancing limit of a piston to raise an alarm.

When abrasions of an inner surface 2A of a disc rotor 2 which is a friction surface between the disc rotor 2 and an outer pad 4, an outer surface 2B of the disc rotor 2, a pad material 4B of an inner pad 4 and a pad material 5B of a back plate 5 progresses and a piston 6 advances to the advancing limit position from a cylinder chamber 3D, a sensor 9 outputs a detection signal to an alarming lamp lighting circuit. By so doing, the alarming lamp lights up or blinks to raise an alarm.