1. A method of reading an original placed on an original support and displaying it, comprising: an image reading step of reading an image of the original placed on the original support to generate an image signal; a placement orientation detection step of detecting placement orientation of said original based on the image signal generated in said image reading step; an image signal rotation step of rotating, when the placement orientation of said original detected in said placement orientation detection step is different from a predetermined orientation, said image signal to said predetermined orientation; and a read image signal display step of displaying the read image signal in an orientation aligned with a predetermined orientation.