This reactor is provided with a coil (2), a magnetic core (3) on which this coil (2) is disposed, and a case that houses an assembly (10) of the coil (2) and magnetic core (3). The case is provided with a bottom plate part (40) constituted of a metal material and side wall parts that are attached to the lower plate part (40) and surround the periphery of the assembly (10). A joining layer (42) that affixes the coil (2) is provided on the inside surface of the lower plate part (40), and the area on which this joining layer (42) is provided has undergone a surface roughening treatment. When anodic oxidation treatment is carried out for the surface roughening treatment, the bottom plate part (40) is provided with an anodic oxidation layer (43). The contact surface area of the bottom plate part (40) and the joining layer (42) is increased by the surface roughening treatment, and the joining strength of the bottom plate part (40) and the coil (2) is increased. By rigidly joining the bottom plate part (40) and the coil (2), the heat of the coil (2) is efficiently transmitted to an installation location by the bottom plate part (40), and heat dissipation characteristics are superior.