To provide a chemical analysis device which extends the life of a light source lamp and ensures measurement accuracy.

In the chemical analysis device, driving power of the light source is set to a lower value than a rated value so as to extend the life of the lamp. However, the driving power of the light source is set so as to keep blank light absorbance within a prescribed allowable value. In addition, the life and breakdown of the light source lamp are diagnosed by monitoring the driving power supplied to the light source. Moreover, breakdown of the light source lamp is also diagnosed by monitoring light absorbance.