A magnetic device includes a magnetic core assembly, a primary winding, a first secondary winding and a second secondary winding. The magnetic core assembly includes a first magnetic cover, a second magnetic cover, a first magnetic leg, a second magnetic leg, a third magnetic leg and a fourth magnetic leg. The primary winding is wound around the first magnetic leg and the third magnetic leg. A first terminal of the first secondary winding is disposed between the first magnetic leg and the second magnetic leg. A second terminal of the first secondary winding is disposed between the third magnetic leg and the fourth magnetic leg. A first terminal of the second secondary winding is disposed between the first magnetic leg and the fourth magnetic leg. A second terminal of the second secondary winding is disposed between the second magnetic leg and the third magnetic leg.