The foaming machine for polystyrene granules "PP-04" is designed for foaming non-foamed polystyrene granules by treating them with saturated water vapor. Non-foamed polystyrene is fed into the heat treatment chamber by a screw feeder. Smooth rotation of the mixing device promotes uniform increase of granules. The device is equipped with a built-in electric steam generator with automatic pumping and heating of water. It can be used both separately and in a technological line for the production of polystyrene concrete or foam plastic. It has the ability to re-foam the granules after curing to achieve the required density.