Abstract: Part of liquefied carbon dioxide is subjected to adiabatic expansion so that the remainder becomes snow-like dry ice due to heat of vaporization and heat of sublimation while a liquid is being sprayed to produce snow-like frozen liquid. The snow-like dry ice and the snow-like frozen liquid are mixed and the mixture is compressed and pelletized to produce hard particles each of which consists of a particle of snow-like dry ice coated with snow-like frozen liquid. Thus obtained particles are projected by compressed air or water under high pressure against an object to be cleaned. Wet type abrasive blasting can be effected because when the particles are projected against the object, the frozen liquid coating the surfaces of snow-like dry-ice particles is broken.