PURPOSE: To obtain a device which is most suitable for reconstitution of a stereoscopical image and spends no time in data gathering, by arranging many photoelectric transducers on the outside of a scintillator in the circumferential direction and the axial direction and leading a generated scintillation light to plural photoelectric transducers.

CONSTITUTION: A cylindrical light guide 2 is attached closely to the outside of a scintillator 1, and many photomultipliers 3 are attached closely to the outside of this light guide 2. A collimator 4 which is ring-shaped as the whole and has many radiation-transmissive holes parallel with each other in each of four directions is arranged freely rotatably in the cylindrical scintillator 1. When gamma rays are made incident to the scintillator 1 through individual holes of the collimator 4, the scintillation light is generated in the scintillator 1 and is led to plural photomultipliers 3 around the light guide 2 by the light guide 2. A position calculating circuit such as a resistance weighted matrix circuit or the like is used, and outputs of individual photomultipliers 3 are led to this circuit to perform the position calculation, thereby detecting the position of generation of the scintillation light.