A pair of regulating guides is disposed on both sides of a conveying belt in a sheet width direction Y, each having a support surface that supports an end edge in the width direction of the sheet conveyed while being nipped by the conveying belt and balls and a guide surface that faces the end edge of the sheet in the width direction. Each of the pair of regulating guides is movable to a first guide position at which the end edge of the sheet in the width direction is supported by the support surface and guided by the guide surface and to a second guide position at which the end edge of the sheet in the sheet width direction is supported by the support surface and which is retracting further away from the end edge in the sheet width direction than the guide position.