A washing machine includes a water tank, a washing tub, a pulsator, a drive motor, a drive shaft, a dewatering shaft that rotates about the same axis of the drive shaft and spins the washing tub, a coupler that is mounted to move up and down along the dewatering shaft and transmits the torque of the drive motor to the dewatering shaft, a solenoid module that moves the coupler upward in a lengthwise direction of the dewatering shaft so as to cut off torque from the drive motor to the dewatering shaft or transmit the torque to the dewatering shaft, when a magnetic field is generated by applying an electric current to a coil, and a coupler guide that rotates itself or fixes the position of the coupler, by coming into contact with the coupler when the coupler moves upward in the lengthwise direction of the dewatering shaft.