A solid ink jet image forming apparatus includes a printing unit which fires melted solid ink onto an image on a printing medium for printing, and an ink supplying unit which contains solid ink in a lateral direction of the printing unit. In the case where the solid ink jet image forming apparatus includes a scanning unit reading an image from a document, a user can simply and easily load the solid ink without moving the scanning unit, so that the solid ink jet image forming apparatus has improved installation stability and a compact size.