To unlock a locked state for an operating member while instantaneously solving an engaged state with a push button in a lock piece constituting a locking mechanism only by operating a thumb turn member on the indoor side.

A push-button type locking and unlocking device is mounted on the outer-wall surface side of the door and brings a lock sliding plate in a pedestal to a movable state through a plurality of the push buttons 6. In the device, a click piece 15 and a lock piece 16 capable of being engaged with at least the push buttons are incorporated into the pedestal. In the device, a driving plate 17 for the click-piece, a locked plate 19 engaged with a stopper 18 in the pedestal and an unlocking plate 21 unlocking the engagement of the stopper 18 so that the locked plate can be rotated are incorporated into the pedestal respectively. When an operating means on the indoor side is operated, the click piece and the lock piece in an engaging relationship with the push buttons are moved in the direction of the unlocking of the engagement through each rotation of the unlocking plate and the driving plate.