PURPOSE: To make an inverting mechanism compact by providing a roller member which is movable in response to the normal/reverse rotation of a conveying belt in the vicinity of an opening part which forms the document invertingly inserting passage of a discharged paper inverting unit.

CONSTITUTION: As a conveying belt is moved rightward, a separating roller 38 is brought into pressure contact with the conveying belt and drivenly rotated while both shaft end parts of the roller 38 move its shaft rightward from the left contacting face of a separating-roller bearing 39, obliquely upward along a guide slope while rotating on their axes. Thereby, the end part of a guide plate 49 which partitions both passages of a document send-out passage 41 and an invertingly inserting passage 42 makes the opening part of the invertingly inserting passage 42 minimum. When the conveying belt 21 is moved leftward, the separating roller 38 is reversed and both shaft end parts of it start to move leftward from the right contacting face of the separating-roller bearing 39 and, while rotating on their axes, the shaft end parts are moved to its left contacting face, where they are only rotated on their axes. Thereby, the invertingly inserting passage 42 can be opened.