A noninvasive blood analyzer is provided which comprises: a light source for illuminating a part of tissues of a living body including a blood vessel; an image pickup section for picking up an image of the illuminated blood vessel and tissues; and an analyzing section for analyzing the picked image; the analyzing section including an extracting section for extracting image density distribution across the blood vessel in the image as an image density profile, a quantifying section for quantifying configurational characteristics of the image density profile, a computing section for computing the concentration of a blood constituent on the basis of the quantified characteristics, and an outputting section for outputting a computation result. The blood analyzer can measure the concentration of blood hemoglobin and the hematocrit in real time with an improved repeatability without blood sampling.