A radiation sensor for the measurement of photo energies of incident radiation is disclosed which comprises a semiconductor substrate sensitive to photons of the incident radiation, at least one common electrode and at least one split electrode, both of which are disposed on the same surface of the substrate, or the common electrode being disposed on one surface of the substrate and the split electrode being disposed on the other surface of the substrate at a diagonal position to the common electrode. Also disclosed is a radiation detecting apparatus using the above-mentioned radiation sensor.