Provided is a heat-transfer-medium heating apparatus including: a first heat-transfer-medium circulating box and a second heat-transfer-medium circulating box, which are attached to each other in a fluid-tight manner, in which heat-transfer-medium circulating paths are formed therein in close contact with both surfaces of a PTC heater; an electrical-component cooling wall member that is provided in, for example, the first heat-transfer-medium circulating box so as to be located adjacent to the heat-transfer-medium circulating path; and an electrical component that is fixed on the electrical-component cooling wall member, wherein a protruding portion is formed on the surface at the heat-transfer-medium circulating path side of the electrical-component cooling wall member so as to be positioned at exactly behind an installation position of the electrical component and to extend towards the heat-transfer-medium circulating path.