Provided is a walking assist device including a main frame configured to be worn by a user, a power unit mounted on the main frame, a pair of power transmission members for transmitting assist force provided by the power unit to femoral parts of the user and a control unit for controlling an operation of the power unit, wherein the control unit comprises a differential angle computation unit for computing a differential angle between angular positions of the femoral parts of the user about respective hip joints of the user a differential angle phase computation unit for computing a differential angle phase according to the differential angle and an assist force computation unit for computing an assist force to be applied to the user according to the differential angle phase.
