A nuclear medicine imaging apparatus according to an embodiment includes a gradation width storage, an estimating unit, and an image generating unit. The gradation width storage is configured to store the gradation width of an image determined by the temporal resolution of a detector. The estimating unit is configured to estimate the spatial position of a positron on the basis of the spatial position of a set of detectors and a set of detection times. The image generating unit is configured to allocate pixel value to pixels corresponding to the gradation width around the estimated spatial position such that a spatial resolution corresponding to the temporal resolution is reflected on a line linking the set of detectors, thereby generating an image.