An image output apparatus is capable of performing index outputting in which reduced images obtained from a plurality of image files are arranged and output. The image output apparatus includes a setting information storage unit configured to store setting information for the index outputting, the setting information being applied to a first-type image file including a plurality of pieces of image data among a plurality of image files as a target of the index outputting, a selecting unit configured to select a piece of image data added with specific information in the setting information from among the plurality of pieces of image data in the first-type image file when an image file as a target of the index outputting is the first-type image file, and an output unit configured to perform the index outputting on the basis of pieces of image data including the selected piece of image data.