PURPOSE: To realize the decrease in fluctuation, by replacing the Braun tube for oscilloscope into the storage type which can store the electron beam producing the scanning luminescent line for a given time and adding the peak display selection switch to the input system.

CONSTITUTION: After confirming the set condition to the object of the γ ray image detector 21 by means of the monitor CRT 28 with the selection of the contact b of the switch 29, the switch is selected to the contact a and the window setting for the peak distribution and the peak analyzer 25 are confirmed. In this case, if the window setting is required for the adjustment, adjustment is made while confirming the window setting condition with the adjustment means of the analyzer 25. The Braun tube of the monitor CRT 28 in this case is suitable for the storage type having the storage time of 10 seconds or less. Further, the contact is selected to b of the switch 29, and after arranging the optimum pick up conditions for scintillation camera, the γ ray image of the recording CRT 23 is picked up with the picture pick up unit. Thus, the fluctuation in the luminescent line constituting the peak distribution of the γ ray energy can be reduced.