The invention discloses a normally-locked hydraulic disc brake device which comprises main clamp body, adjusting screw plug, limit screw, piston, limit location step, first sealing ring, second sealing ring, spring, third sealing ring, fourth sealing ring and positioning screw, step guiding hole and threaded hole are arranged in the main clamp body, adjusting screw plug is connected at bottom of the main clamp body through the threaded hole, adjusting gasket is arranged between the adjusting screw plug and the main clamp body, piston is pressed into the step guiding hole through matching, limit screw is connected at bottom of the adjusting screw plug through threads, spring is arranged in step guiding hole of the large shaft end, the piston is provided with first groove and second groove outside the large shaft end, first sealing ring and second sealing ring are respectively arranged in the first groove and the second groove, the piston is provided with third groove and fourth groove outside the small shaft end, and third sealing ring and fourth sealing ring are respectively arranged in the third groove and the fourth groove. The overall structure design of the invention is ingenious and convenient to use.