There is provided a single particle detection technique based on the scanning molecule counting method which individually detects single particles using light measurement with a confocal or multiphoton microscope, where the existences of a non-light-emitting particle and a light-emitting particle can be detected while being discriminated from one another in a sample solution. The inventive technique of detecting a single particle detects light from a light detection region during moving the position of the light detection region of the microscope in a sample solution containing a non-light-emitting particle and a light-emitting particle to generate time series light intensity data; and detects in the time series light intensity data a light intensity increase relative to background light intensity as a signal indicating the existence of the light-emitting particle and a light intensity reduction relative to the background light intensity as a signal indicating the existence of the non-light-emitting particle.