An image forming apparatus includes a printing portion, a receiving portion, an image reading portion for reading one surface and another surface connected to the one surface of a material to be housed, so as to generate individual image data of the one surface and the another surface, and a controlling portion configured to recognize a size of the material to be housed based on the individual image data, to generate paper bag image data that is image data of a development of the paper bag in which the entire of the material to be housed can fit, the development being with tabs for sticking for assembly, and to control the printing portion to print the development with tabs for sticking based on the paper bag image data.