Semiconductor ZnS thin films have been deposited by a chemical bath deposition (CBD) on a glass substrate at 80 degrees C with different deposition time (4, 6 and 8 h), The films have been further studied in order to determine the change in optical and electrical properties as a function of deposition time. The film thicknesses have been calculated between 210 - 1375 nm by using gravimetrical analysis. The optical properties of ZnS thin films have been determined by transmittance (%T) and absorbance (A) measurements by UV-Vis spectroscopy operated wavelength range between 300 and 1100 nm at room temperature. The optical transmittance values of ZnS thin films in the visible region of the electromagnetic spectrum have been found to be between 51-90%. The calculations indicate that the refractive index (n) in the visible region is between 1.40 and 2.45. The optical band gaps (E-g) of thin films have been calculated between 3.61-3.88 eV while the band edge sharpness values (B) are varied between 6.95 x 10(9)-8.96 x 10(10) eV/cm(2). The specific resistivity values (p) of the films are found to be between 1.08 x 10(5)-1.01 x 10(6) Omega.cm and exhibit an n-type conductivity by Hall measurement.