A walk assist robot for lower body walking of a walking trainee, including a joint angle signal measurement unit disposed on a joint of the walking trainee, an electromyogram (EMG) signal measurement unit disposed on a muscle related to ankle joint extension of the walking trainee, a plantar pressure signal measurement unit disposed on a sole of the walking trainee, and a control unit to recognize signals measured from the joint angle signal measurement unit, the EMG signal measurement unit and the plantar pressure signal measurement unit and process the signals to recognize a walking speed intention of the walking trainee, wherein the control unit controls a walking speed of the walk assist robot from the walking speed intention of the walking trainee.