The present invention provides a radiation measurement device, which shortens periodic interruption periods in the radiation measurements and prevents damage to the amplifier, and a nuclear medicine diagnosis system using such measurement device. The radiation measurement device comprises a semiconductor radiation detector detecting a radiation, a capacitor, which applies voltage to the semiconductor radiation detector, one or more direct current power supplies each capable of making either of positive and negative electric charge collect on one of the electrodes of the capacitor, a constant-current device, which conducts an electric current from the direct current power supplies to the one of the electrodes of the capacitor, and two or more switching devices installed in the wiring connecting the direct current power supplies and the one of the electrodes of the capacitor. Further disclosed is a nuclear medicine diagnosis system equipped with such radiation measurement device.