An image reading apparatus includes a control unit configured to perform advance obtainment processing for obtaining correction data for shading correction by using a reading unit, in a state in which a document is placed on a document tray and before accepting a document read start instruction. The control unit includes, as operation modes for the advance obtainment processing, a first mode for obtaining the correction data by performing the advance obtainment processing using the second resolution in a case where the second resolution is designated as the reading resolution, and a second mode for obtaining the correction data by performing the advance obtainment processing using the first resolution in a case where the second resolution is designated as the reading resolution.