Abstract: An apparatus according to the invention is for treating waste materials of foam resin products having been used mainly as packing or wrapping materials, which is provided with a crushing room furnishing stationary cutting edges and rotatably moving cutting edges at the lower part of a hopper into which the waste foam resin materials are thrown, and at the outside of the crushing room, a cylindrical volume shrinking mechanism which receives the destroyed resin products and send them in succession, heats to soften and fuse them one another, and effecting heat and pressure thereto so as to de-foam and extrude the resin like a hot chewing cake or a hot birdlime. The cylindrical volume shrinking mechanism has an extruding nozzle opening upward, from which the resin is charged into a metal mold cylinder and when this charging amount reaches to a certain level, the operation of the cylindrical volume shrinking mechanism is stopped.