Abstract: A gamma camera sensitivity correction device and method which utilizes the fact that the collimator's characteristic correction coefficients do not change with time, wherein first of all the collimator's characteristic sensitivity data are found, and then freshly collected detector characteristic uniformity data are found with the collimator removed. From the collimator's characteristic sensitivity data and detector's characteristic uniformity data, uniformity data in the condition that the collimator is mounted on the detector are derived. Then, correction coefficients are determined based on these derived uniformity data. In this way, the uniformity correction matrix for sensitivity correction can be found with a small radiation source in a short time.