A sheet processing system, comprising: a tray configured to support a sheet on opposite sides of the sheet orthogonal to a conveyance direction of the sheet, the tray including a first adjustable support and second adjustable support positioned opposite the first adjustable support in the direction orthogonal to the conveyance direction of the sheet, the first and second adjustable supports being independently movable in the direction orthogonal to the conveyance direction; a skew sensor configured to detect a skew angle of the sheet conveyed to the tray; a corner sensor configured to detect positions of each corner on a front end in the downstream direction of the sheet conveyed to the tray; and a controller configured to control movement of the first and second adjustable supports based on the detected skew angle and the detected positions of each corner on the front end of the sheet conveyed to the tray so that the sheet is conveyed to the tray without jamming; wherein the corner sensor is configured to rotate through a predetermined angle in a plane of the sheet; the controller is further configured to: control a rotation of the corner sensor based on the detected skew angle so that the corner sensor is parallel to the front end of the sheet conveyed to the tray when the corner sensor detects the positions of each corner on the front end of the sheet conveyed to the tray and move the first adjustable support to a position X in the direction orthogonal to the conveyance direction of the sheet given by X = s × cos A − L × tan A − M, and the controller moves the second adjustable support to a position Y in the direction orthogonal to the conveyance direction of the sheet given by Y = t × cos A − L × tan A + M, where s is the detected position of a first corner of the front end of the sheet, t is the detected position of a second corner of the front end of the sheet, A is the detected skew angle, L is a predetermined constant calculated in advance for expanding an interval between the first and second adjustable supports as A becomes large, and M is a predetermined constant calculated in advance for maintaining a margin between the corners of the front end of the sheet and the corresponding adjustable supports. a tray configured to support a sheet on opposite sides of the sheet orthogonal to a conveyance direction of the sheet, the tray including a first adjustable support and second adjustable support positioned opposite the first adjustable support in the direction orthogonal to the conveyance direction of the sheet, the first and second adjustable supports being independently movable in the direction orthogonal to the conveyance direction; a skew sensor configured to detect a skew angle of the sheet conveyed to the tray; a corner sensor configured to detect positions of each corner on a front end in the downstream direction of the sheet conveyed to the tray; and a controller configured to control movement of the first and second adjustable supports based on the detected skew angle and the detected positions of each corner on the front end of the sheet conveyed to the tray so that the sheet is conveyed to the tray without jamming; wherein the corner sensor is configured to rotate through a predetermined angle in a plane of the sheet; the controller is further configured to: control a rotation of the corner sensor based on the detected skew angle so that the corner sensor is parallel to the front end of the sheet conveyed to the tray when the corner sensor detects the positions of each corner on the front end of the sheet conveyed to the tray and move the first adjustable support to a position X in the direction orthogonal to the conveyance direction of the sheet given by X = s × cos A − L × tan A − M, and the controller moves the second adjustable support to a position Y in the direction orthogonal to the conveyance direction of the sheet given by Y = t × cos A − L × tan A + M, where s is the detected position of a first corner of the front end of the sheet, t is the detected position of a second corner of the front end of the sheet, A is the detected skew angle, L is a predetermined constant calculated in advance for expanding an interval between the first and second adjustable supports as A becomes large, and M is a predetermined constant calculated in advance for maintaining a margin between the corners of the front end of the sheet and the corresponding adjustable supports. control a rotation of the corner sensor based on the detected skew angle so that the corner sensor is parallel to the front end of the sheet conveyed to the tray when the corner sensor detects the positions of each corner on the front end of the sheet conveyed to the tray and move the first adjustable support to a position X in the direction orthogonal to the conveyance direction of the sheet given by X = s × cos A − L × tan A − M, and the controller moves the second adjustable support to a position Y in the direction orthogonal to the conveyance direction of the sheet given by Y = t × cos A − L × tan A + M, where s is the detected position of a first corner of the front end of the sheet, t is the detected position of a second corner of the front end of the sheet, A is the detected skew angle, L is a predetermined constant calculated in advance for expanding an interval between the first and second adjustable supports as A becomes large, and M is a predetermined constant calculated in advance for maintaining a margin between the corners of the front end of the sheet and the corresponding adjustable supports.