An analyzing device mixes a sample liquid with a reagent by rotation of the analyzing device about a rotation center to generate a centrifugal force. A measurement cell is formed so as to extend in a direction along which the centrifugal force is applied, and a capillary area to which the sample liquid is sucked by a capillary force is formed on one of the side walls of the measurement cell, the side walls being arranged in a rotational direction. The capillary area extends from the outer periphery position to the inner periphery of the measurement cell, thereby reducing the size of the analyzing device. Further, the sample liquid in the measurement cell is sucked to the capillary area by slowing or stopping a rotation, and then the rotation is accelerated to return the sample liquid in the capillary area to the measurement cell.