A spring force of a thrust spring can be determined independently of a spring force of a locking spring, reducing an operating load of an unlocking operation. A locking device includes a locking mechanism provided on one of two members to be engaged with each other, and a striker provided on the other of the two members. The locking mechanism includes a base plate, a hook, a pawl, a cam, a locking spring, a thrust spring and a canceling plate. The base plate has a recess that is capable of receiving the striker. The hook, when rotated relative to the base plate, is capable of forming a locked condition in which the striker is held between the hook and the recess of the base plate or an unlocked condition in which the hook is spaced away from the striker. The pawl is capable of rotating relative to the base plate and maintaining the hook in the locked condition. The cam is capable of further pressing the hook in the locked condition toward a locking direction. The locking spring is capable of biasing the hook and the pawl such that the hook and the pawl are stabilized in the locked condition or the unlocked condition. The thrust spring is capable of biasing the cam in a direction to press the hook. The canceling plate is rotatably supported via a shaft of the hook and is coaxially rotatable with the hook. The canceling plate has a movable range in which the canceling plate can rotate relative to the hook and has a contacting portion that is capable of contacting the striker within the movable range when the hook is in the locked condition.