An automatic analysis apparatus measures a concentration of an intended component in a biological sample, such as blood or urine, or determines whether such component is contained in the sample or not, and includes a function such that, with respect to the optical system, a part whose lifetime has ended is specified or the degree of deterioration of a part is detected to provide a user with the information. The automatic analyzer has a storage unit for storing a transmitted light distribution for a plurality of wavelengths detected by a receptor element for transmitted light which has passed through a substance to be measured, and a control unit for comparing a first, stored transmitted light distribution with a second transmitted light distribution acquired at the time of measurement to determine a deteriorating part from a plurality of parts based on the result of the comparison and output the result.