Abstract: A reactor of the present invention includes a coil 2, a magnetic core 3 in which the coil 2 is disposed, and a case that stores a combined product 10 made up of the coil 2 and the magnetic core 3. The case includes a bottom plate portion 40 made of a metal material, and a sidewall portion that is attached to the bottom plate portion 40 to surround the combined product 10. A joining layer 42 that fixes the coil 2 is provided at the inner face of the bottom plate portion 40. The region provided with the joining layer 42 has been subjected to surface roughening treatment. When anodic oxidation treatment is carried out as the surface roughening treatment, the bottom plate portion 40 includes an anodic oxide layer 43. The surface roughening treatment increases the contact area between the bottom plate portion 40 and the joining layer 42, whereby the joining strength between the bottom plate portion 40 and the coil 2 can be enhanced.