A relay device includes mechanical relays, a first bus bar, a second bus bar, and a relay drive circuit. The relay includes a coil, a moving contact whose position changes according to whether the coil is energized, a load terminal conductive to the contact and connected to the first bar, and a coil terminal connected to the coil and second bar. The first bar includes a loading circuit. A current flows to an external load through the loading circuit opened/closed when the position of the contact changes. The second bar includes a coil circuit through which the coil is energized. The drive circuit is packaged on the second bar and opens/closes the coil circuit based on an operation signal. The first and second bars are stacked at predetermined intervals. The relays are between the first and second bars.