A mold clamping apparatus provided with at least one forceful mold opening mechanism, the apparatus comprising: a base; a stationary platen fastened to the base; a mold clamping mechanism which is placed in parallel with the stationary platen, and which is supported by the base so as to be freely movable; a movable platen placed between the mold clamping mechanism and the stationary platen; at least one tie bar which is extended from the stationary platen and which passes completely through the movable platen and through the mold clamping mechanism; a mold opening and closing mechanism that moves the movable platen along the at least one tie bar; and a control unit that controls the mold opening and closing mechanism and the mold clamping mechanism, wherein the mold clamping mechanism is provided with at least one half nut and the at least one tie bar is provided with a circumferential groove to be meshed with the at least one half nut, wherein the at least one forceful mold opening mechanism is provided across the movable platen and the mold clamping mechanism and opens the molds (22, 23) at an initial stage of mold opening, wherein the at least one forceful mold opening mechanism is set so as to have greater axial force and a shorter stroke than the mold opening and closing mechanism, and wherein the control unit controls opening and closing of the at least one half nut, controls the at least one forceful mold opening mechanism, and also controls a position of the at least one half nut in such a way that the at least one half nut is synchronized with the circumferential groove by the at least one forceful mold opening mechanism. a base; a stationary platen fastened to the base; a mold clamping mechanism which is placed in parallel with the stationary platen, and which is supported by the base so as to be freely movable; a movable platen placed between the mold clamping mechanism and the stationary platen; at least one tie bar which is extended from the stationary platen and which passes completely through the movable platen and through the mold clamping mechanism; a mold opening and closing mechanism that moves the movable platen along the at least one tie bar; and a control unit that controls the mold opening and closing mechanism and the mold clamping mechanism, wherein the mold clamping mechanism is provided with at least one half nut and the at least one tie bar is provided with a circumferential groove to be meshed with the at least one half nut, wherein the at least one forceful mold opening mechanism is provided across the movable platen and the mold clamping mechanism and opens the molds (22, 23) at an initial stage of mold opening, wherein the at least one forceful mold opening mechanism is set so as to have greater axial force and a shorter stroke than the mold opening and closing mechanism, and wherein the control unit controls opening and closing of the at least one half nut, controls the at least one forceful mold opening mechanism, and also controls a position of the at least one half nut in such a way that the at least one half nut is synchronized with the circumferential groove by the at least one forceful mold opening mechanism.