An electrostimulator includes a boost circuit supplying a stimulus signal, first and second electrodes disposed on a skin surface, detecting a voluntary myoelectric signal and giving the stimulus signal, an amplification circuit amplifying the voluntary myoelectric signal, a controller controlling the stimulus signal in accordance with the voluntary myoelectric signal, an H-bridge circuit including first and third switches connected in series and connected to the second electrode, and second and fourth switches connected in series and connected to the first electrode, the first to the fourth switches being connected in parallel, an isolated DC-DC converter supplying a power to the controller and the amplification circuit, a regulator outputting a midpoint voltage of a power-supply voltage, and a third electrode connected to the regulator and a reference terminal of the amplification circuit and disposed on the skin surface.