Radiation image detection device

A radiation image detecting device configured to detect fluorescence light emitted from a recording medium with a radiation image recorded therein by applying excitation light to the recording medium, comprising:

• a photodetecting element that detects the fluorescence light;
• and
• a prism that is disposed so as to be located on an optical path of the excitation light traveling toward the recording medium and between the photodetecting element and the recording medium,
• wherein the prism includes, as surface thereof, a first surface that is opposed to the recording medium and a second surface and a third surface that are inclined relative to the first surface, the prism being disposed so that the excitation light incident through the second surface propagates inside and is output from the first surface and so that reflection from the recording medium incident through the first surface propagates inside and is output from the second surface or from the third surface, and
• wherein the photodetecting element is disposed so as to be opposed to a region different from a region where the reflection from the recording medium is output, in the surface of the prism.