An image forming apparatus includes an image data conversion unit configured to convert print data into bitmap data, a sheet feeding unit configured to store and feed a sheet on which printing is to be performed, a detecting unit configured to detect an orientation of the sheet in the sheet feeding unit, a print unit configured to print the bitmap data onto the sheet fed from the sheet feeding unit, a determination unit configured to determine whether or not a data orientation in which pieces of pixel data of the bitmap data are arranged matches the sheet orientation detected by the detecting unit, and an image rotating unit configured to rotate the bitmap data when the determination unit determines that the data orientation does not match the sheet orientation, whereby the data orientation matches with the sheet orientation.