To provide a reactor with which resin can fully be packed between a core and a coil with ease, and in which the core can easily be handled when the reactor is manufactured. The reactor includes: a coil 10 formed with paired coil elements 10A and 10B that are made of a spirally wound wire, the coil elements being coupled to each other in a paralleled state; internal core portions 22 that are fitted into the coil elements 10A and 10B to structure a part of an annular core 20; and exposed core portions 24 that are exposed outside the coil elements 10A and 10B to couple the internal core portions 22 to each other, to thereby form the rest of the annular core 20. The reactor includes an external resin portion that covers at least a part of an assembled product 1A made up of the coil 10 and the core 20. In each of the exposed core portions 24, a cut-out corner portion 24g is provided to at least part of a joining portion of an inner end face 24f facing the end face of the coil and an adjacent face (side face 24s) that is continuous to the inner end face 24f, whereby the resin can easily be packed between the coil 10 and the core 20, and it becomes possible to prevent chipping off when handled.