Crystalline Sb2Te3 thin films of different thicknesses have been prepared by subsequent annealing (at 500 K) of vacuum deposited, as-grown, amorphous thin films of Sb2Te3 prepared on glass substrates at room temperature. Thermoelectric power and electrical resistivity of these annealed (crystalline) films have been determined as a function of temperature. The size dependence of thermoelectric power and electrical resistivity have been analyzed by the effective mean free path model of size effect. It is found that both the thermoelectric power and the electrical resistivity are linear functions of the reciprocal of thickness of the films. The data from the analyses of thermoelectric power and electrical resistivity have been combined to evaluate important material parameters such as carrier concentration, their mean free path, Fermi energy, and effective mass. The values of some of these are compared with the previous available values from literature.