A reactor including an assembly of a coil, a magnetic core on which the coil is disposed, and a case that houses the assembly. The case includes an installation face, a side wall that is removably attached to the installation face and surrounds the periphery of the assembly, and a heat dissipation layer formed on the inner face of the installation face and interposed between the installation face and the installation-side face of the coil. The installation face consists of aluminum, the side wall consists of an insulating resin, and the heat dissipation layer consists of an adhesive with high thermal conductivity and excellent insulation. The installation face is separate from the side wall, making it easy to form the heat dissipation layer, and having excellent heat dissipation. The side wall consists of an insulating resin, thus reducing the gap between it and the coil.