A corner cut apparatus for entering into a transport path for transporting a sheet in a crossing direction to cut corners of the sheet includes a cut blade frame that supports a cut blade shifting with respect to the sheet surface, a receiving blade frame that supports a receiving blade for receiving the shifting cut blade, and a drive member that causes the cut blade frame and the receiving blade frame to enter into the transport path of the sheet, where blade shapes of the cut blade and the receiving blade are a back-to-back shape with an entry direction as a reference line. By this means, it is possible to provide the apparatus for cutting corners at the lead edge and end edge of the sheet in an inclined or curved manner, only by shifting (up and down) the blade with respect to the sheet surface.