To provide a nuclear medicine diagnostic apparatus capable of detecting the position of a marker without using radioactive isotope as the marker.

A marker having a large attenuation coefficient of gamma rays is mounted on a body surface of a subject P and a radiation detector 3 detects radiation emitted by the radioactive isotope administered in the subject. A first reconstitution section 21 reconstitutes projection data detected by the radiation detector 3 by a filter back projection method to generate first reconstitution image data. A marker detection section 30 generates reference image data by pixels having minus pixel values out of pixels constituting the first reconstitution image data. A display control section 7 displays a reference image and a medical image acquired by another imaging device on a display section 51.