A lock device is improved in durability by operating the operation member of a boom lock device in a non-contact state to solve a problem in a conventional work machine because there is a problem that the operation member is worn at the lateral rotating part of a boom bracket. In the lock device 51 for locking a boom 16 of the excavating device to the main body, an engaging member is provided on one of the boom and a boom bracket 15 provided on the main body, and an engaged member is provided on the other of the boom and the boom bracket. The engaging member is constituted by a plate formed on one side thereof with a hook part 52a, and on the other side thereof with a slot 52c. A support pin 55 is inserted into the slot, and a stopped 53 is disposed above the support pin, so that the support pin 55 and the stopper 53 support the engaging member.