A surface heater body which is constructed as two-layer, expanded partial composite laminated body and contains two mutually separated channels or channel systems adjoining one another wall-to-wall in a heat-conducting manner; one channel system which extends over the entire area of the surface heater body and which is hermetically closed off, operates as heat-pipe to distribute the supplied heat over a large area; a heat channel traversed by heating water extends along the bottom edge of the surface heater body; a rectilinear continuous non-expanded strip is provided between the heat channel and the heat-pipe channel system, along which the partial composite laminated body is bent U-shaped so that the heat channel and the heat-pipe channel system come into mutual abutment where they are permanently and heat-conductingly connected with each other over the entire contact surface; a separate pipe may also be provided as heat channel or, as a still further alternative, a heat-pipe may be inserted into the heat-pipe channel system whereby the two edges of the surface heater body are sealed off at the places where the heat pipe leaves the heater element.