An image forming apparatus settable for a custom size or a standard size includes an index sheet setting section, a print engine control processing section, and a print execution processing section. The index sheet setting section sets information pertaining to an index sheet having an index tab. Based on the information set by the index sheet setting section, the print engine control processing section switches between control in accordance with a setting for the custom size and control in accordance with a setting for the standard size. The print execution processing section executes control of printing on the index sheet.