Reactor

A reactor comprising:

• a reactor main body which comprises a core formed of a powder magnetic core, a resin member having the core embedded therein, and a coil wound around an outer circumference of the resin member;
• a casing which comprises a bottom surface and a side wall standing upright from the bottom surface, and which houses therein the reactor main body;
• and
• a filler molding portion which is formed of a cured filler, and which fastens the reactor main body to the casing,
• wherein the resin member is provided with:
• a bottom opening which is provided at a location facing the bottom surface of the casing and where the coil is not wound, and which exposes the core;
• and
• a back-side opening which is provided at a location orthogonal to a winding direction of the coil and facing the side wall, and which exposes the core, and
• wherein the back-side opening is provided with an exposing portion that is not covered with the filler molding portion and is exposed.