A power supply device includes a transformer, a primary semiconductor component, a secondary semiconductor component, a choke coil and a circuit board. Electronic components which include the transformer, the primary semiconductor component, the secondary semiconductor component, and the choke coil, are stacked in pairs, in a normal direction of a board. One pair forms a first stacked body and another pair to forms a second stacked body. A circuit board is interposed between the one pair of electronic components which forms the first stacked body, and also between the other pair of electronic components which forms the second stacked body.