A locking device includes a lever turnably provided relative to a lid member, and switched from an initial state to an operating state against an urging force or self-weight; a lock rod sliding in association with turning of the lever; and a braking device. The locking device locks the lid member in a main member side through the lock rod, and switches the lid member to be unlocked by turning of the lever. The braking device is a rotation damper including a braking shaft with a gear, and placed to approximately conform to a turning center of the lever relative to the lever to damp the lever and the lock rod. The rotation damper includes an operation gear disposed to engage the gear of the rotation damper, associate the gear with sliding of the lock rod, and rotate the gear in a direction opposite to the turning of the lever.