To obtain an image reader that has a uniform resolution of an image and eliminates the need for a memory for software processing by focusing with a constant magnification in synchronism with a scanning of a scanning means.

The rotating mirror 22 of an image pickup camera section acts like a scanning means and is driven to scan an original image in the subscanning direction by a driver. An image pickup lens 23 is driven by the driver to form an image on a line sensor 21 and is focused without changing an image pickup magnification even when the distance from the image forming position to an original face is changed. The focusing with a constant magnification is performed in synchronism with a scanning by the rotating mirror 22. Two-dimensional image reading is conducted by reading in the subscanning direction and reading in the main scanning direction by the line sensor 21 itself. Thus, even when the height of a book original B differs for each read position, the read image is not distorted like a barrel and an image equivalent to an original image is obtained.