The invention relates to a mold-closing unit for an injection molding machine for processing plastics, comprising a mold-moving device for moving the movable mold support into and out of closure of an injection mold. At least one force transmission element is connected to the movable mold support and at its end remote from the movable mold support has a section (14a) which is assigned to the stationary mold support. The stationary mold support (10) is assigned a locking device (15) having a plurality of locking elements (70) which can be moved into interlocking operative connection with the actuatable section (14a). The locking device (15) has at least one actuator (16) which is movable in the closing direction (s-s) and on which, during movement of the actuator, the locking elements (70) are movable transversely to the closing direction (s-s) along a sliding block guide (60) in and out of an interlocking operative connection with the actuatable section (14a). The actuator is at the same time connected to at least one piston (18) of a piston-cylinder unit (17) for applying the closing force.