REACTOR

Provided is a reactor including a coil, and a core having an inner core portion arranged inside the coil and an outer core portion covering the outside of the coil. The inner core portion of the reactor has a higher saturation magnetic flux density than that of the outer core portion. The outer core portion has a lower permeability than that of the inner core portion, and is made of a mixture of a magnetic material and a resin. The case has a heat-transfer portion at an inner wall surface, as a heat-radiation structure for at least one of the coil and the inner core portion. With the reactor, even if the outside of the coil is covered with a core member, heat generated in the reactor can be effectively dissipated.