To improve the precision of an automatic focus by acquiring an image more suitable for automatic focusing in an image reader reading an image for automatic focusing with an image sensor.

An image sensor 13 is moved to a position of a film image on a screen in an automatic focus state to acquire its image. Then a control section 18 discriminates a negative/positive image on the basis of image data, a luminous energy of a light source 1 is changed, an amplification factor of an amplifier 23 is controlled, or a reference voltage of an A/D converter 14 is controlled according to the discrimination result. Then a focus lens 19 is driven under the above condition, the focus is calculated by the obtained image data to conduct automatic focusing.