Provided is an image reading apparatus that instantaneously executes functions and settings with the setting of a document on a platen glass, and an image forming apparatus. The image reading part according to the present disclosure includes a platen cover, an opening and closing detecting part, and an operation executing part. The document placing position detecting part acquires position placing data by pre-scan of a scanner, when opening of the platen cover is detected, after the opening of the platen cover is detected, and detects a placing position of a document placed on the platen glass based on the acquired placing position detecting data. The operation executing part receives selection of functions corresponding to the placing position detected by the document placing position detecting part and executes the selected function.