To provide an image reading apparatus for enabling an optical carriage movably supported in a rail member to be locked reliably in a predetermined position of an apparatus frame without causing failure by shock in transport, one of the apparatus frame and optical carriage is provided with a lock member traveling between a release position and a lock position, and a biasing member for biasing the lock member in a predetermined direction, and the other one is provided with an engagement receiving portion being fitted with an engagement portion formed in the lock member. Then, the engagement portion and the engagement receiving portion are configured to inhibit movements in the scanning direction of the optical carriage in the lock position, and the biasing force of the biasing member is concurrently configured to act on the carriage in the direction orthogonal to the scanning direction so as to increase friction between the carriage and a traveling rail.