An optical analysis method of detecting light from a light-emitting probe (218, 222) binding to a particle dispersed and moving at random in a sample solution to detect the particle by using an optical system of a confocal microscope or a multiphoton microscope, comprising steps of: preparing the sample solution containing the particle and the light-emitting probe (218, 222); moving a position of a light detection region of the optical system in the sample solution by changing an optical path of the optical system; and detecting light from the light detection region while moving the position of the light detection region in the sample solution, characterized in that the method comprises the further steps of detecting individually and simultaneously with moving the position of the light detection region a light signal from the light-emitting probe (218, 222) having bound to each particle in the detected light to detect individually the particle(s) by detecting individually in the light intensity data, as the signal of one light-emitting probe (218, 222), a variation in time of a light intensity (Em) having a profile expected in the light from one light-emitting probe (218, 222) which moves relatively in an inside of the light detection region, counting the number of the individually detected particle(s) to count the number of the particle(s) detected while moving the position of the light detection region, and associating the number of detected particle(s) with a moving amount over which the position of the light detection region has been moved to acquire information on the number density or concentration of the particle(s) in the sample solution, wherein, in the step of moving the position of the light detection region, the position of the light detection region is moved at a velocity higher than a diffusional moving velocity of the light-emitting probe (218, 222) having bound to the particle. preparing the sample solution containing the particle and the light-emitting probe (218, 222); moving a position of a light detection region of the optical system in the sample solution by changing an optical path of the optical system; and detecting light from the light detection region while moving the position of the light detection region in the sample solution, characterized in that the method comprises the further steps of detecting individually and simultaneously with moving the position of the light detection region a light signal from the light-emitting probe (218, 222) having bound to each particle in the detected light to detect individually the particle(s) by detecting individually in the light intensity data, as the signal of one light-emitting probe (218, 222), a variation in time of a light intensity (Em) having a profile expected in the light from one light-emitting probe (218, 222) which moves relatively in an inside of the light detection region, counting the number of the individually detected particle(s) to count the number of the particle(s) detected while moving the position of the light detection region, and associating the number of detected particle(s) with a moving amount over which the position of the light detection region has been moved to acquire information on the number density or concentration of the particle(s) in the sample solution, wherein, in the step of moving the position of the light detection region, the position of the light detection region is moved at a velocity higher than a diffusional moving velocity of the light-emitting probe (218, 222) having bound to the particle.