PURPOSE: To avoid the damage of a book and to simplify the constitution of an optical system by putting a book on a gable roof-shaped original platen using the platen glass at one side and reading the book.

CONSTITUTION: A gable roof-shaped original platen 11 is provided at the upper part of a copying machine 10 of a reading device. The platen 11 consists of a platen glass 12 having a 45° inclination and a mirror 13 having a 135° inclination. The vertical angle θ of the platen 11 is set at 90°. A light source unit 16 consisting of a light source 14 and a reflector 15 is set at a place near the lower surface of the glass 12 so that it can have reciprocating motions along the slope of the glass 12. While a reading element unit 19 consisting of a reading element 17 and a lens 18 is provided at the lower part of the mirror 13 so that it can have reciprocating motions in the same direction as the unit 16. Then a book 51 is put on the platen 11 and read by reciprocating motions of both units 16 and 19. This can avoid the damage of the book 51 and also simplifies the constitution of an optical system.