An improved resin denture base molding apparatus for molding denture bases by injecting fused resin R into a denture base plaster mold formed in a flask F, wherein the improvement includes a table 2 provided in a manner capable of elevating up and down along a plurality of vertical guide rods 1, an elevation driving mechanism 3 for elevating the table 2, an upper support member 6 provided horizontally across each upper end of the guide rods 1 and having a through hole 4, a spring storing section 7 provided at the location of the through hole 4 on the upper surface of the upper support member 6, a push spring 8 stored in the spring storing section 7, a piston rod 10 inserted in the through hole 4 and urged downwardly by the push spring 8 and having a resin pressurizing piston 9 at the lower end thereof, a flask F placed on the table 2 and having a resin filling hole 11 at the top thereof, a cylinder 13 having a resin passage 12 that communicates with the resin filling hole 11 at the bottom wall thereof and is located below the piston 9 and a pressure breakable member 14 disposed within the cylinder 13 so that it covers the resin passage 12.