A radiation image detector includes an up-conversion phosphor layer for emitting fluorescence by irradiation with infrared light, a first electrode layer for transmitting the infrared light, the fluorescence and radiation carrying a radiation image, a photoconductive layer for recording, a charge storage portion, a photoconductive layer for readout, and a second electrode layer for transmitting the infrared light and the readout light. Radiation is recorded as latent image charge in the charge storage portion. The electric charge is read out from the charge storage portion by irradiating the photoconductive layer for readout with the readout light from the second electrode layer side. The up-conversion phosphor layer is irradiated with the infrared light from the second electrode layer side and remaining charge in the vicinity of the first electrode layer is erased by fluorescence emitted from the up-conversion phosphor layer by irradiation with the infrared light.