To provide a document reader capable of reducing the power consumption of a switching mechanism in a rotational direction of a conveyance roller.

A document length measuring unit 81 measures a document length. A switching roller 19 or 23, which can switch a rotational direction to one of a forward rotation state and a backward rotation state, conveys a document. A rotational direction control unit 84 controls the rotational direction. The switching roller 19 or 23 consumes greater power in the backward rotation state than that in the forward rotation state. Further, the rotational direction control unit 84 controls the rotational direction on the basis of the document length so as to shorten time for setting the backward rotation state when the document length is short.