An image forming apparatus includes a scanning device and a printing device. The scanning device and the printing device are configured to be separately arranged when the image forming apparatus is in use. The printing device includes a control unit that transmits and receives signals to and from a plurality of units included in the scanning device, and a power supplying unit that supplies electric power to the units. The scanning device includes a first relay substrate that receives electric power from the power supplying unit and distributes the electric power to the units, and relays signals between each of the units and the control unit.