To provide a hydraulic cutter, a movable blade of which can be returned to an original position without being damaged, even if the movable blade is not retreated upon release of oil pressure.

The hydraulic cutter includes: a cylinder block 11 having a piston 14 which is advanced by oil pressure of hydraulic oil h supplied from a tank 7 and which is retreated when the oil pressure is released; a head 30 having a fixed blade 31 arranged in the further front of the advanced piston 14, the movable blade 32 to be advanced toward the fixed blade 31 together with the piston 14 and guide parts 38, 39 for guiding the movable blade 32 to be advanced/retreated; and projection parts 41, 42 which are arranged to be projected respectively from the side faces 32a, 32b of the movable blade 32 and used for imparting impact force, in abnormal times, to such a direction that the movable blade 32 is retreated.