Abstract: A radiation image readout apparatus scans an excitation light in a main scanning direction and a sub scanning direction over a stimulable phosphor sheet, on which radiation energy has been stored, and detects the stimulated emission emitted thereupon; wherein, various types of phosphor sheets can be read out at a high resolution and high sensitivity. The excitation light energy level for obtaining an adequate sensitivity for each type of phosphor sheet is obtained. A controller controls the intensity of the excitation light emitted from the light source and the speed of the scanning mechanism, that is, the readout speed, whereby the excitation light projected onto a phosphor sheet of which the diffusion rate has been controlled by the inclusion therein of an navy blue colorant is of a greater energy level than the excitation light projected onto the white stimulable phosphor sheet not containing the navy blue colorant.