According to one embodiment, a nuclear medicine diagnosis includes a light signal generating unit, photodetection unit, measurement unit, calculation unit, and storage unit. The light signal generating unit repeatedly generates light signals. The photodetection unit repeatedly generates first output signals corresponding to intensities of the light signals, repeatedly generates second output signals corresponding to intensities of gamma rays emitted from a subject. The measurement unit repeatedly measures light signal detection times and repeatedly measures gamma ray detection times. The calculation unit calculates a difference between a target gamma ray detection time and a target light signal detection time of the light signal detection times for each of the gamma ray detection times. The target light signal detection time is measured before the target gamma ray detection time. The storage unit stores the calculated difference in association with a target second output signal of the second output signals.