An injection molding machine device and a pneumatic support mechanism, the injection molding machine device includes a rack, at least one guide rail fixed to the rack, at least two guide rods, a fixed mold base fixed to one end of the rack, a movable mold base arranged opposite to the fixed mold base, at least one pneumatic support mechanism, and a cylinder. Both ends of each guide rod are fixed to the rack. The movable mold base has at least two receiving holes for receiving the guide rods, and slides on the guide rods. The pneumatic support mechanism has a lower support plate positioned above the guide rail, and an upper support plate fixed to the movable mold base. At least one accommodating cavity is arranged between the upper and lower support plates to receive the cylinder. The height of the movable mold base is adjustable by the cylinder.