A nuclear medicine diagnostic apparatus according to an embodiment includes processing circuitry configured to perform control to execute gamma ray acquisition for main imaging for a subject, and prior acquisition to acquire gamma rays in a plurality of acquisition positions in the subject prior to the main imaging, calculate values of gamma ray acquisition time for respective imaging positions in the main imaging, based on count values of gamma rays acquired in the prior acquisition, and perform control to execute the main imaging, based on the calculated values of the gamma ray acquisition time for the respective imaging positions.