An energy transmission device includes: a semiconductor device formed on a first semiconductor substrate; a semiconductor integrated circuit including a reverse current preventing diode and a control circuit; a DC voltage source; and a transformer. The reverse current preventing diode includes a reverse current preventing layer of a second conductivity type formed at a surface of a second semiconductor substrate, and a well layer of a first conductivity type formed in the second semiconductor substrate and covering the reverse current preventing layer. The transformer includes a primary winding connected in series with the semiconductor device and the DC voltage source, and a first secondary winding connected to a load. The energy transmission device is configured so that electric power is supplied from the first secondary winding of the transformer to the load. A second drain electrode of the semiconductor device is electrically connected to the reverse current preventing layer.