Reactor and method of manufacturing the same

A reactor comprising:

• a coil including a wire that is covered with an insulating film and is wound, the coil having an inner side and an outer side and including on the outer side a first lateral surface and a second lateral surface different from the first lateral surface;
• a cooler that faces the first lateral surface;
• and
• an insulating heat radiation layer that is sandwiched between the first lateral surface and the cooler, wherein
• in the first lateral surface, the wire is not covered with the insulating film
• in the second lateral surface, the wire is covered with the insulating film, and
• a degree of flatness of the first lateral surface is lower than a degree of flatness of the second lateral surface, wherein the degree of flatness of the respective lateral surface of the coil is represented by a distance between a respective plane S1, that is on the respective lateral surface in contact with a winding turn of the coil defining an innermost portion of the respective lateral surface and a respective plane S2 that is on the respective lateral surface in contact with a winding turn of the coil defining an outermost portion of the respective lateral surface, the plane S1 and the plane S2 being parallel to each other, wherein the degree of flatness being lower meaning that there is a shorter distance between plane S1 and plane S2 for the first lateral surface, as compared to a distance between plane S1 and plane 2 of the second lateral surface.