Provided is a reactor in which it is possible to reduce molding failures in inner resin portions when molding the inner resin portions. A reactor includes: a coil having winding portions; and a magnetic core having inner core portions and outer core portions. The reactor further includes: inner resin portions that fill gaps between the winding portions and the inner core portions; and inner interposed members that are interposed between the winding portions and the inner core portions, and form resin flow paths. The inner interposed members have spacers arranged between the winding portions and the inner core portions. The spacers are provided with air discharge paths that are in communication with the resin flow paths, and extend in the axial direction of the winding portions to at least one end face side of the winding portions.