Abstract: A reactor-use component which provides improved workability in assembling into a reactor, and a reactor using the component are provided. The reactor-use component is for structuring a reactor including a coil 10 formed with a pair of paralleled coil elements 10A and 10B made of a spirally wound wire and a core 20 fitted into the coil elements 10A and 10B to form an annular shape. The reactor-use component includes an internal resin portion 30 that retains a shape of the coil 10, and hollow bores 30h formed by a part of the internal resin portion 30 for fitting the core 20 to inner circumferences of the coil elements 10A and 10B. By inserting internal core portions 22 into the hollow bores 30h and joining opposite ends of the internal core portions 22 to exposed core portions 24, the reactor 1 can be obtained. Because the internal resin portion 30 retains the coil 10 in a state incapable of expanding or compressing, the workability in assembling into the reactor 1 can be improved.