A non-invasive blood analyzer contains a light applicator for illuminating a detection region under the skin of a living body including a blood vessel; a camera for capturing an image of the illuminated detection region; an analyzer for processing the captured image and analyzing at least a component of blood in the blood vessel; a transparent plate; and a support for supporting the transparent plate and contacting the transparent plate closely with the skin over the detection region. The light applicator and the camera are constructed to illuminate the detection region and capture the image of the detection region through the transparent plate. Further, a drive controller is included for driving the support to move the transparent plate contacted closely with the skin in order to adjust the detection region to thereby compensate for any change in position of the blood vessel.