A compact reactor with excellent productivity and heat dissipation is provided. Reactor 1α includes a coil formed by spirally winding a wire 2w and a magnetic core 3 having an inside core portion inserted into the coil and an outside core portion 32 coupled to the inside core portion. These core portions form a closed magnetic circuit. The coil is covered with an inside resin portion 4 on the outer circumference thereof to form a coil molded unit 20α with its shape being held. The outer circumference of a combination unit 10 of the coil molded unit 20α and the magnetic core 3 is covered with an outside resin portion 5α. Reactor 1α does not have a case and is thus compact. A surface of the outside core portion 32 on the installation side (core installation surface 32d) is exposed form the outside resin portion 5α and is in direct contact with a fixed object, thereby achieving excellent heat dissipation. The provision of the coil molded unit 20α facilitates the handling of the coil during assembly of reactor 1α, thereby achieving good productivity.