To enhance image quality and to realize automatic page turning by means of simple configuration by providing a member which is moved along the surface of a facing-page original so as to turn over a page, measuring a position in a member height direction concerning a height distribution in pace-facing direction and executing a reading operation corresponding to the height distribution.

CPU 101 measures the heights of an original surface in respective line positions by moving a page turning roller a little ahead of the sub- scanning of image picking-up by a line sensor 31 and calculates a lens position corresponding to the height and a distortion correcting quantity (variable magnification rate). A calculated value is stored in RAM 105 to generate a control table T1. An image forming lens is arranged in an adequate position immediately before sub-scanning reaches a target line by referring to the control table T1 and also the distortion correcting quantity as against the target line is given to an image processing circuit 103. A book scanner 1 measures and manages height distribution information by a measurement system 150 consisting of a position sensor 81, a height sensor 82, CPU 101 and RAM 105.