A plurality of reaction containers each being charged with an agitation ball made of a magnetic material are circularly arranged on a reaction disk so as to be supplied with a reagent and a sample. The reaction disk is driven reciprocatingly at a small amplitude for a predetermined time so as to cause the reaction containers to be vibrated arcuately each time a new reaction container is supplied with the reagent. As a result of the vibration of the reaction containers, the agitation balls in the respective reaction containers vigorously move to agitate the reaction solutions in the respective reaction containers. A photometric device is disposed so as to apply a light to the reaction container thereby to allow a fluorescent or absorbance photometric measurement. In the reaction container brought to the photometric measuring position, the agitation ball is attracted to the wall of the reaction container so as to be kept away from the path of light in the photometric device.