PURPOSE: To improve the sensitivity of a scintillation camera by a relatively easy method by using a collimator which has plural linear focuses in the direction of the axis of rotation of the detector of the scintillation camera to a subject.

CONSTITUTION: The collimator 7 has a convergence point 12 only in an X-axial direction and no convergence point in a Y-axial direction and is a parallel collimator. Then convergent lines 13 forming the convergence point 12 form plural plural visual fields of the scintillation camera in a wedgelike shape 15 for the subject. While the scintillation camera detector which includes this collimator 7 is rotated about the axis of rotation, information on γ rays emitted by the subject 14 at each angle is collected to improve the sensitivity by the relatively easy method.