A method of producing inorganic semiconductor- and phosphor-primary particles, which each comprises forming the particles by reacting at least one kind of precursor solution of the inorganic primary particle in a solvent, of which major component is water of a reacting vessel, under the conditions that the pressure is 0.2 to 20 MPa and the temperature is 120.degree. C. to 370.degree. C.; and inorganic semiconductor- and phosphor-primary particles produced by the method.