Provided is a heating device which makes it possible to effectively perform heat exchange between a heating element and a heat medium without increasing the number of components, and further to eliminate air retention and increase of a pressure loss. A heating device 1 is constituted of a case 2 including therein a flow path 3 through which a heat medium flows, and an electric heating wire heater 4 disposed in the flow path of the case to heat the heat medium. The case comprises a first case section 6 and a second case section 7 each of which has at least one opened surface and which are connected to each other in a state where respective openings are made to abut on each other, and a plate-like gasket 8 which is interposed between abutment portions of the first case section and the second case section, and seals a space between both the case sections, and the gasket controls the flow of the heat medium in the flow path.