A folder/gluer unit includes an upper transfer belt that transfers a corrugated sheet in a direction of transfer, a pair of forming belts that abut against a folding surface which is formed by folding both end portions of the corrugated sheet in a width direction orthogonal to the direction of transfer and fold both of the end portions of the corrugated sheet in the width direction, a pair of folding bars that are disposed in the direction of transfer, abut against the folding surface at both of the end portions of the folded corrugated sheet in the width direction, and guide both of the end portions of the corrugated sheet in the width direction, a moving mechanism that moves the pair of folding bars in the width direction and in a vertical direction, and a control unit that controls the moving mechanism to adjust a position of the folding bar.