A mold assembly for an injection-molding machine for molding a disc, including a stationary die (10, 84), a movable die (20, 88) movable relative to the stationary die, a stamper (30, 98) which is retained at least at an outer peripheral portion (31) thereof on the movable die and which has information signals recorded thereon, and an outer retainer ring (45, 102) for retaining the stamper on the movable die at the outer peripheral portion. The stationary die, stamper and outer retainer ring cooperate to define a mold cavity (C, 90), so that the disc is molded of a resin material injected into said cavity, such that the information signals are reproduced on one surface of the molded disc. The mold assembly has an annular void (S, 126) in which an outer peripheral edge of the outer peripheral portion of the stamper is accommodated without a contact with the movable die and the outer retainer ring. The mold assembly may further has a suction space (106, 136) which communicates with the stamper and/or the mold cavity, and which is connected to an external suction source, to discharge gases trapped in the mold assembly.