The present invention relates to a blood vessel wall analyzing apparatus provided with a structure enabling accurate measurement of plaque components in a blood vessel wall in a state that reduces the burden on a patient. In the blood vessel wall analyzing apparatus (1), measurement light is illuminated onto a measured portion within a blood vessel such as a carotid artery (C) from a light illuminating unit (30) provided outside the blood vessel, while light from the measured portion is detected in a light receiving unit (40) provided outside the blood vessel. Thus, since the status of the blood vessel wall can be analyzed without inserting an apparatus involved in measurement into the blood vessel, the burden on the patient is reduced during measurement. In addition, as a result of carrying out measurement using near infrared light (a light component in the wavelength range of 780 nm to 2750 nm) that exhibits characteristics that differ according to the compositions of substances such as plaque adhered within the blood vessel, analysis can be carried out that distinguish compositions such as plaque using an analyzing apparatus provided outside the blood vessel.