PROBLEM TO BE SOLVED : To provide a technology for accurately quantitating cerebral blood flow in a non-invasive manner.SOLUTION : A cerebral blood flow quantitation device 100 comprises : an image acquisition part 20 for acquiring an image to be obtained by applying radiopharmaceuticals to a subject, that is, a two-dimensional nuclear medicine image 10 including at least brain, lung, and pulmonary artery of the subject; a region setting part 60 for setting a first region of interest including at least a part of the brain, a second region of interest including at least a part of the lung, and a third region of interest including at least a part of the pulmonary artery in the two-dimensional nuclear medicine image; and a cerebral blood flow quantitation part 70 for, on the basis of pixel intensity in each of the first region of interest, the second region of interest and the third region of interest, quantitating the inclination of a graph obtained by plotting a ratio of a value based on pixel intensity in the first region of interest to a value based on pixel intensity in the second region of interest with respect to a ratio of a value based on pixel intensity in the third region of interest to a value based on pixel intensity in the second region of interest as cerebral blood flow in the first region of interest.SELECTED DRAWING : Figure 1COPYRIGHT : (C)2019, JPO&INPIT