To provide a walking assist device which can apply torque to a knee joint at a suitable timing. A walking assist device includes an actuator, a reaction force sensor and an angle sensor. The walking assist device is fitted to a user's leg. The actuator is able to apply torque to a knee joint of one leg of the user. The reaction force sensor detects a reaction force that the foot of the one leg receives from the floor. The angle sensor detects a hip joint angle of the one leg around a pitch axis. The walking assist device specifies a timing to start applying the torque to the knee joint in a direction that swings the lower leg backward, based on the detected reaction force and the detected hip joint angle.
