AUTOMATIC ANALYSIS DEVICE

The invention provides an automatic analyzer having a scattered-light detecting optical system in which a light source is disposed at an angle with respect to a plane of a reaction vessel. This reduces the amount of a sample-reagent mix required for an analysis, thereby reducing the running cost of reagents as well, and also allows relatively free design of reaction vessels in terms of their sizes and shapes. The automatic analyzer includes: a reaction vessel in which a sample is caused to react with a reagent; a reaction disk on which to place reaction vessels in the form of a circle; a reaction disk rotating mechanism for rotating the reaction disk; a light source for radiating light to be measured onto one of the reaction vessels; and a photodetector for detecting transmissive light radiated from the light source and passing through a sample-reagent mix in the one of the reaction vessels. The automatic analyzer further includes an optical system for causing the light source to radiate light onto one of the reaction vessels at an angle with respect to a plane of the one of the reaction vessels.