An image reading apparatus capable of occurring no failure in reading of the original document sheet due to a change in the original document sheet conveyance conditions that occurs in switching a pair of rollers of document conveyance mechanism from a separated state to a contacted state by including a document reader, a document conveyance mechanism including a pair of rollers that are disposed upstream from a reading position in terms of a direction of document conveyance and a controller for, when a trailing edge of one original document sheet has passed the reading position, switching the pair of rollers of the document conveyance mechanism from a separated state to a contacted state before a leading edge of a next original document sheet reaches the reading position.