To be adapted to various types of latex reagents for detecting scattered light and thereby measuring agglutination reactions with high sensitivity while sufficiently ensuring integration time. To be adapted to various types of latex particles of different particle sizes, a plurality of light receivers are arranged in a plane perpendicular to the direction of cell movement by rotation of a cell disk. To ensure sufficient integration time, the angle between the optical axis of the irradiation light and each of a plurality of optical axes of scattered light viewed from above the cell is made equal to or less than 17.7° including a mounting error.