Abstract: A lock device of a cover, especially of a hatch cover of a personal watercraft, having operation members disposed on a lower surface of the cover which is locked by an engagement with a hold pin and is released by a releasing operation of the operation members. The locking device includes a frame member having operation members located at both sides of and under the lower surface of the cover. The frame member further includes, a pair of slide members each of which slides in a direction away from the operation member by the releasing operation of each of the operation members, a moving member which is caused to move in the direction perpendicular to the sliding direction of the sliding members in response to the sliding movement of either one or both of the slide members, and an engaging member which moves together with the moving member to move into an engaging hole for engaging the hold pin.