An injection foam molding machine according to the present invention includes: a clamping unit that moves a movable die plate 3 relative to a fixed die plate 2 to clamp the die plates; a fixed side mold attached to the fixed die plate 2; a movable side mold attached to the movable die plate 3; a plurality of drive units 50 that widen an interval between both of the die plates 2 and 3; and a die-plate-interval adjusting unit 60 that adjusts a distance over which the movable die plate 3 is moved by the drive units 50, and when a molten foam resin is foamed, an inner-side interval within the mold cavity is determined, and thus an accurate molded product can be obtained.