In a wearable motion assist device, a motion assist device for generating a motion pattern synchronized with a wearer while maintaining a certain phase difference between a motion of the wearer and a motion of the device, and a synchronization based control method for the device are provided. The motion assist device acquires a phase of torque generated by the wearer's motion, applies a value of the phase to a phase oscillator model as an input, performs arithmetic processing, and calculates target torque and a target angle of the device with the motion of the device synchronized with the wearer. It is possible to improve an assisting effect of the device by controlling the device based on the calculated values.
