The preparation and characterization of (Cd,Zn)S thin films were attempted using two kinds of chemical bath deposition process : all the reactants were mixed either at room temperature (process A) or after preheating the source solutions (process B). The band gaps and the lattice constants of the thin films prepared by process B changed from the values for CdS to those for ZnS, but those of the films prepared by process A were not changed. X-ray diffraction analyses showed that all the peaks from the thin films prepared by process B could be assigned to diffraction lines of wurtzite (Cd,Zn)S. The photoconductivity of the thin films was larger than the dark conductivity, in particular 5 X 10(3) times larger in the thin films prepared by process B with [Zn]/([Cd] + [Zn]) = 0.9 in the solution.