An image forming apparatus is described. The image forming apparatus may include a first casing and a second casing above the first casing. The second casing is provided with an upper surface including a generally horizontal surface, a lower surface extending beyond the upper surface in a generally horizontal direction and a side surface connecting an end edge of the upper surface and an end edge of the lower surface with each other over the whole area. The first casing is provided with an upper surface coming into contact with the lower surface of the second casing over the whole area and a side surface including a generally vertical surface. An inclined surface connecting the generally vertical surface of the first casing and the generally horizontal surface of the second casing with each other, is provided continuously along the first casing and the second casing.