To provide an image reader which improves a reading speed when document is read in black-and-white more than when it is read in color and also can reduce power supply capacity.

An image reader 11 comprises three kinds of light sources R, B and G which emit light of red, blue and green respectively, a photoelectric converter 16 which converts incident light into electric charge, an optical system 15 which guides light that is emitted from the light sources to document 19 and makes reflected light incident on an optical converting means 16 and a selecting means 13 which selects either of a black-and-white mode that reads an image in black-and-white or a color mode that reads the image in color. The reader 11 is also provided with a controlling means 1 which controls the turning on/off of the light sources R, B and G, and when the black-and-white mode is selected by the means 13 and an image of the document 19 is read, the means 1 also selects two kinds of light sources B and G or G and R among three kinds of light sources R, B and G and simultaneously turns on two kinds of these selected light sources B and G or G and R.