A reactor is provided with: a magnetic core which includes a coil having a winding part, an inner-side core part disposed inside of the winding part, and an outer-side core part disposed outside of the winding part; and an outer-side interposing part that is interposed between an end surface of the winding part and an inner end surface of the outer-side core part. The winding part includes: a winding body; and a melt-fusion layer that is provided to the outer circumference of the winding body and mutually joins adjacent turns. The reactor is also provided with a fixation-prevention structure for preventing the end surface of the winding part and the outer-side interposing part from becoming fixed to each other by the melt-fusion layer.