Provided is a walking assist device including a seat member, a leg link having a joint portion, and a driving source for the joint portion. The walking assist device allows a user to rest by sitting on the seat member. Accordingly, the walking assist device further includes a lock mechanism disposed in the joint portion and an operation unit for the lock mechanism. When the operation unit is switched on, the driving source is controlled to increase an up-pushing force on the seat member. A variation rate on the up-pushing force is increased with time to a given value where the lock mechanism is initiated.