A remote particle counter comprising a pulsed laser generator, laser light emitting optics, scattered light collecting optics, a high-sensitivity two-dimensional photo detector as a scattered light detecting portion having a fast gating capability such as a CCD camera, and a control and measure system, wherein suspended fine particles forming aerosols in the atmosphere which are far away from the site of laser emission are illuminated with laser light, the resulting backward scattered light from the individual fine particles is detected as image, and the number and size distribution of the suspended fine particles are measured at a remote site.