PURPOSE: To provide the electronic picture reader utilizing effectively a dynamic range of an A/D converter without saturation by adjusting the gain of an amplifier so as to obtain an optimum luminous quantity even when a luminous quantity distribution of a lamp is changed due to a change with lapse of time.

CONSTITUTION: The reader is provided with an optical system collecting a reflected light from an edge white reflecting board 12 of an original read window 11 with illumination from a light source, an image sensor 14 converting the incident light into an electric signal for each picture element, an amplifier 15 amplifying the signal, and an A/D converter 21 converting the signal into a digital signal. Prior to reading of a document, when a reference white level board is read, a means controlling an amplifier gain adjustment circuit 25 to adjust a gain of the amplifier 15 so as to use effectively the dynamic range of the A/D converter 21 while taking the luminous quantity distribution attended with deterioration in a lamp for original radiation into account is built in the CPU 27.