A mold-clamping mechanism in which top and bottom tie bars extend between a pressure-receiving platen and a fixed platen fixed to a bed, a movable platen is movably attached to the tie bars, a toggle link extends between the movable platen and the pressure-receiving platen, the movable platen is moved toward the fixed platen by the toggle link, and a mold is clamped by the movable platen and the fixed platen. The pressure-receiving platen includes a bottom part surrounding a central cavity, and a ceiling part for joining respective top ends of left and right wall parts provided upright from both ends of the bottom part. An opening via which the cavity communicates with the outside is provided to the bottom part and the ceiling part.