The invention provides nuclear medicine diagnosis device, form tomography diagnosis device, nuclear medicine data arithmetic processing method, and from tomogram arithmetic processing method. In a state in which a subject is absent, blank data (S1) is collected by a self-radioactivity element typified by Lu-176. In a state in which the subject is present, transmission data is collected by the self-radioactivity element (S2). Emission data is collected by gamma rays emitted from the subject injected with a radiopharmaceutical (S3). Absorption-corrected data is calculated based on the blank data and the transmission data (S4 to S7), and the emission data is absorption-corrected using the absorption-corrected data (S8). Although such background data obtained by the self-radioactivity is originally abandoned, the background data is rather used for the absorption-corrected data. Stable absorption correction can be thereby conducted.