A sheet processing apparatus includes: first to third pairs of conveying members; and a bifurcating claw that moves to a first guiding position for guiding the sheet to the second pair of conveying members, a second guiding position for guiding a deflected portion of the sheet to the third pair of conveying members, and a third guiding position for guiding a leading end of the sheet to the third pair of conveying members. The second pair of conveying members is rotated backward in a state in which the sheet is held by the first pair of conveying members and the second pair of conveying members, to guide the deflected portion to the third pair of conveying members and cause the deflected portion to be folded by the third pair of conveying members.