To improve reliability of return prohibiting means to a first sheet conveying passage in a sheet reversing and conveying device.

The return prohibiting means 16 comprises a gate member having a fixed guide member 16a arranged between the first sheet conveying passage 4 and a second sheet conveying means 8, an elastic part 16b with one end mounted on the fixed guide member 16a and another end arranged to block the first sheet conveying passage 4 and a returning face part 16c to return itself to a direction facing the fixed guide member 16a to the elastic part 16b. When a sheet is guided by first sheet conveying means 4a, 4b, the elastic part 16b is pressed by the sheet to be deformed elastically to an opening direction of the first sheet conveying passage 4. When the sheet is conveyed reversely by the first sheet conveying means 4a, 4b, the sheet is moved along the returning face part 16c to prohibit returning to the first sheet conveying passage 4.