A reactor including: a coil including a winding portion formed by winding a winding wire; and a magnetic core that forms a closed magnetic circuit constituted by an inner core portion located inside the winding portion and an outer core portion located outside the winding portion. The reactor further includes an inner resin portion that fills a gap between the inner circumferential surface of the winding portion and the outer circumferential surface of the inner core portion, and when a side, of the outer core portion, that faces the inner core portion is defined as an inner side, and the opposite side is defined as an outer side, the outer core portion is provided with a through hole that is open to both the inner side and the outer side, and the through hole is filled with a portion of the inner resin portion.