A reactor which may be employed in an inverter for automotive vehicles. The reactor includes a coil, a core, a casing, and a positioning member. The core is made of a solidified magnetic powder/resin mixture and has the coil embedded therein. The positioning member is disposed in the casing to position the coil relative to the casing and equipped with fins configured to stir the magnetic powder/resin mixture before solidified. Specifically, the positioning member is designed to perform two functions: one is to fix the location of the coil within the casing, and the other is to stir the magnetic powder/resin mixture through the fins, thus eliminating the need for removing a portion of the magnetic powder/resin mixture adhered to the fins, which leads to improved productivity of the reactor.