PURPOSE: To produce the titled CdS having high crystallinity and composed of nonagglomerated particles having uniform surface, by introducing H2S into an aqueous solution of hydrochloric acid containing CdSO4, mixing the resultant CdS with an alkali metal chloride, and calcining the mixture.

CONSTITUTION: 0.3W0.7mol/l of CdSO4 is dissolved in 1W2N aqueous solution of hydrochloric acid, and H2S is introduced into the solution to obtain CdS containing CdSl2 as a flux. The CdS is mixed with 5W40wt% of an alkali metal chloride (e.g. NaCl) and calcined at 500W550°C. The photocondutive CdS obtained by this process has decreased amount of crystal defects possible to form an energy level trapping the photon carrier near the surface.