In case of both sides printing, the sheet S having an image formed on the obverse surface is conveyed to the first reversal section of the reversal device 50 disposed in a reversal path R3. In the first reversal section, the sheet S is conveyed to a U-turn reversal path by the reversal roller 56 with the first side section of the sheet S as the leading edge section. In the U-turn reversal path, a position of the first side surface section and a position of the second side surface section of the sheet S are exchanged and the sheet S is conveyed to the second reversal section. In the second reversal section, the sheet having been turned over is fed again to the register rollers 16 with a leading edge section at image forming on the obverse surface as the leading edge side. Whereby the same edge of the sheet S contacts with the register rollers 16 when the image is formed on the obverse side and when the image is formed on the reverse side.