The invention relates to a casement closure device for a door or casement, especially of switch cabinets or the like, comprising a housing (10) which can be fixed on the door leaf or on the cabinet body. The closure device also comprises a key-operated lock cylinder (13) which is arranged in said housing, and a locking tongue (19) which can turn between an unlocking position and a locking position. The aim of the invention is to produce a casement closure device exhibiting a tightening torque which is as large as possible. To this end, the lock cylinder (13) is uncoupled from the locking tongue (19), is locked in the housing (10) when the key is removed, and can be removed from the housing (10) when the key is inserted and moved to the unblocking position. In addition, the locking tongue (19) which is held on the housing (10) comprises an actuation opening (20) for engaging an actuating means which can be inserted in the housing channel (12) in a positive locking manner, said channel being free when the lock cylinder (13) is removed from the housing (10).