A reactor includes a coil having a winding portion, and a magnetic core including a core piece having an inner core portion disposed inside the winding portion. The core piece is a compact made of a composite material that contains a magnetic powder and a resin. The reactor further includes: a first projection that is integrated with and projects from an outer peripheral face of the inner core portion, and comes into contact with an inner peripheral face of the winding portion so as to position the winding portion in a diameter direction of the winding portion, and a second projection that is integrated with and projects from the core piece at a position opposing an end face of the winding portion, and comes into contact with the end face of the winding portion so as to position the winding portion in an axial direction thereof.