According to an embodiment, a radiation detection device includes a scintillator layer, a plurality of detectors, a setting unit, an identifier, and a corrector. The scintillator layer is configured to convert radiation into scintillation light. The detectors are arranged along a first surface facing the scintillator layer to detect light. The setting unit is configured to set one of the detectors as a first detector to be corrected. The identifier is configured to identify, out of the detectors, a second detector that detects a synchronization signal synchronizing with a first signal detected by the first detector. The corrector is configured to correct an energy spectrum of light detected by the first detector on the basis of a second signal serving as the synchronization signal in signals detected by the second detector, the first signal, and characteristic X-ray energy of a scintillator raw material constituting the scintillator layer.