The invention relates to an electric therapeutic instrument, which mainly consists of a support plate, a pedal, a screw rod, a screw, a first positioning shaft, a second positioning shaft, a motor shaft and an electric motor. The angle between the pedal and a back supporting plate of the support plate can be changed by regulating the length, penetrating through the tail end of a cylindrical screw nut, of the screw rod; when a patient generates lower limb spasticity, the electric therapeutic instrument can be regulated to the angle capable of being accepted by the patient; the foot sole tightly abuts against the pedal, and the knee straightening state is maintained; the electric therapeutic instrument helps the patient to extend the lower limb and foot sole muscles to relieve the pain; and the reduction of the relying on medical personnel is facilitated.