Provided is a walking assist device capable of changing a battery to be used without decreasing a capability to assist walking. A walking assist device 100 comprises a leg attachment 10, a battery 50, and a controller 12. The leg attachment 10 has an actuator for applying torque on a joint of one leg of a user. The battery 50 supplies electric power to the actuator. The battery 50 (a first battery) is configured by a plurality of battery cells 51a, 51b, and 51 c being connected. A battery in which at least one battery cell is electrically separated from the first battery corresponds to a second battery. The controller 12 changes a power source of the actuator from the first battery to the second battery while the other leg is making contact with ground.
