The utility model provides a cover locking device which can effectively utilize the space in a vehicle. According to the cover locking device (10) provided by the utility model, the rear end part of a locking part (50) is accommodated in a housing (11) and a sealing part (33) is utilized to cover the rear part of the housing (11), so that the locking part (50) does not protrude backwards out of the housing (11). Moreover, the sealing part (33) is clamped with a tab clamping groove (14B) of a main housing (12) to be supported not to move forth and back, and thus, the locking part (50) is reliably prevented from protruding backwards out of the housing (11). In addition, intensity of the housing (11) is improved and the linear movement of the locking part (50) is stable.