PURPOSE: To obtain the titled CdS contg. no coarse particles and giving a clear image when used as an electrophotographic sensitive material by introducing hydrogen sulfide or the like into an aqueous soln. contg. Cd ion while keeping the pH of the soln. constant to precipitate CdS particles.

CONSTITUTION: By introducing gaseous hydrogen sulfide or the like into an aqueous soln. contg. Cd ion such as an aqueous soln. of cadmium sulfate, CdS particles are formed by precipitation to manufacture photoconductive CdS. At this time, by continuously adding an alkali soln. simultaneously with the introduction of gaseous hydrogen sulfide, the aqueous soln. is neutralized, and the hydrogen ion concn. of the soln. is kept constant. In order to keep the hydrogen ion concn. constant during the precipitation reaction, an alkali metallic sulfide such as Na2S, K2S or Li2S may be used in place of hydrogen sulfide, or an OH type ion exchange resin may by charged continuously. Thus, CdS particles are prevented from being made larger in particle size, and the titled CdS having a uniform particle size is obtd.