The invention provides a small-sized automatic analyzer being compact, enabling a large number of analysis items to be carried out, and having a high processing speed. The automatic analyzer is particularly suitably applied to a medical analyzer used for qualitative/quantitative analysis of living body samples, such as urine and blood. A plurality of sample dispensing mechanism s capable of being operated independently of each other are provided to suck a sample from any one of a plurality of sample suction positions and to discharge the sucked sample to any one of a plurality of positions on a reaction disk. The automatic analyzer having a high processing capability can be thus realized without increasing the system size.