Abstract: Radiation doses ranging from a very weak level to a very high instantaneous level can be monitored real-time by, a differential and integral type of radiation measuring apparatus in a convenient and precise manner using a stimulable phosphor as a radiation detecting medium. The radiation detecting portion comprises in planar superposition a bundle of laterally radiating optical fibers, a stimulable phosphor, an optical filter centered at the wavelength of fluorescence, and a-bundle of wavelength shifting optical fibers sensitive to the wavelength of stimulated fluorescence. On the basis of two actions of the stimulable phosphor, one for emitting stimulated fluorescence in proportion to the dose of incident radiation upon illumination with exciting light and the other for emitting prompt fluorescence upon excitation by the incident radiation, the radiation detecting portion selectively detects stimulated fluorescence and prompt fluorescence at specified time intervals.