An optical analysis device comprising a confocal microscope or a multiphoton microscope, the optical analysis device being configured to detect light from a plurality light-emitting particles dispersed and moving at random in a sample solution using an optical system of the confocal microscope or the multiphoton microscope and further comprising: a light detection region moving means which is configured to conduct a movement, at a speed which is higher than the speed of the particles due to Brownian motion, of a position of a light detection region of the optical system along a predetermined route in the sample solution by changing an optical path within the optical system; a light detecting means which is configured to detect light from the light detection region; and a signal processing means which is configured: to generate time series light intensity data of the light from the light detection region detected with the light detecting means during moving the position of the light detection region in the sample solution, and to individually detect a respective plurality of signals indicating light respectively emitted from each of a plurality of the light-emitting particles in the time series light intensity data; to control the light detection region moving means to conduct a cyclical movement of the position of the light detection region along the predetermined route for at least two cycles, to use the time series light intensity data obtained during the cyclical moving of the position of the light detection region along the predetermined route for the at least two cycles to detect in each of the at least two cycles respective light signals defined as representative value data belonging respectively to each of the plurality of light-emitting particles in each of the at least two cycles; and to determine, for each particle at least one respective representative value light intensity from the respective representative value data. a light detection region moving means which is configured to conduct a movement, at a speed which is higher than the speed of the particles due to Brownian motion, of a position of a light detection region of the optical system along a predetermined route in the sample solution by changing an optical path within the optical system; a light detecting means which is configured to detect light from the light detection region; and a signal processing means which is configured: to generate time series light intensity data of the light from the light detection region detected with the light detecting means during moving the position of the light detection region in the sample solution, and to individually detect a respective plurality of signals indicating light respectively emitted from each of a plurality of the light-emitting particles in the time series light intensity data; to control the light detection region moving means to conduct a cyclical movement of the position of the light detection region along the predetermined route for at least two cycles, to use the time series light intensity data obtained during the cyclical moving of the position of the light detection region along the predetermined route for the at least two cycles to detect in each of the at least two cycles respective light signals defined as representative value data belonging respectively to each of the plurality of light-emitting particles in each of the at least two cycles; and to determine, for each particle at least one respective representative value light intensity from the respective representative value data. to generate time series light intensity data of the light from the light detection region detected with the light detecting means during moving the position of the light detection region in the sample solution, and to individually detect a respective plurality of signals indicating light respectively emitted from each of a plurality of the light-emitting particles in the time series light intensity data; to control the light detection region moving means to conduct a cyclical movement of the position of the light detection region along the predetermined route for at least two cycles, to use the time series light intensity data obtained during the cyclical moving of the position of the light detection region along the predetermined route for the at least two cycles to detect in each of the at least two cycles respective light signals defined as representative value data belonging respectively to each of the plurality of light-emitting particles in each of the at least two cycles; and to determine, for each particle at least one respective representative value light intensity from the respective representative value data.