There is provided an optical analysis technique of detecting light of a light-emitting particle in a sample solution in the scanning molecule counting method using the light measurement with a confocal or multiphoton microscope, for suppressing the scattering in detected results of signals of light of light-emitting particles smaller and achieving the improvement of accuracy. The inventive technique comprises moving the position of a light detection region along a predetermined route for multiple circulation times by changing the optical path of the optical system; detecting light from the light detection region and generating time series light intensity data during the moving of the light detection region and detecting individually a signal indicating light from each light-emitting particle existing in the predetermined route using the time series light intensity data obtained in the circulating movements of the light detection region of multiple times.