A blood flow image diagnosing device of the present invention includes a laser light irradiation system for applying laser light to an observation region of a biotissue having blood cells a light receiving section having a plurality of pixels and adapted to detect reflection light from the observation region of the biotissue an image capturing section for successively capturing a plurality of images on the basis of a signal from the light receiving section an image storage section for storing the plurality of images a computation section for computing the speed of blood flow within the biotissue from time course changes of output signals of the pixels throughout the stored images and a display section for displaying a two-dimensional distribution which is the result of the computation as a blood flow map. The computation section includes a pigment concentration correction section for correcting the blood flow map obtained as a result of computation in accordance with the pigment concentration of the observation region.
