Disclosed herein is an image forming apparatus, including: a language analysis unit for analyzing print data and generating data having an intermediate format between the print data and bitmap data generated based on the print data; an image processing unit for rasterizing the generated data having the intermediate format for each band by using the predetermined number of lines and generating the bitmap data; a memory for holding the data for which rasterizing processing is being performed by the image processing unit; a printing unit for performing printing based on the generated bitmap data; and a number-of-line switching unit for switching the number of lines of the band in the rasterizing processing of the image processing unit according to whether the print data is data that can include transparency processing data or not.