A sheet-through document reading apparatus including: a document tray for containing a plurality of documents; a determination unit that determines a length of a document on the document tray; a feed unit that separates and feeds a document on the document tray; a resist convey unit that performs consistency processing on the document fed by the feed unit; a first drive unit that rotationally drives the resist convey unit; a read convey unit that feeds the document subjected to consistency processing by the resist convey unit; a second drive unit that rotationally drives the read convey unit; a reading unit that reads, at a fixed reading position, the document conveyed by the read convey unit; and a control unit for changing a relative conveying velocity between the resist convey unit and the read convey unit on the basis of a result of the determination by the determination unit.