To provide floor substrate material for floor heating, particularly suited to concrete-construction houses, capable of freely corresponding to various room layouts and the shapes of rooms, allowing easy floor level setting and floor heating execution in one process, providing an excellent effect of the floor heating.

A plastic floor substrate material is provided with piping grooves 12 for a heat source on an upper surface of a substrate 10 of a predetermined size, and the upper surface including the piping grooves 12 is covered with a thin metal plate 14 with good heat conductivity. The structural base 10 can be obtained by foam molding an alloy of polystyrene or polystyrene and other resin. A straight line grooves to house a straight pipe for the heat source and a curved groove to house a bend pipe for the heat source are prepared for the piping grooves 12.