In this work we report on phase transformation of 304 stainless steel thin films due to heat treatment. Ex-situ annealing was applied for evaporated 304 stainless steel thin films inside an ultra-high vacuum chamber with a pressure of 3 x 10(-7) Pa at temperatures of 500 degrees C and 600 degrees C. The structure of thin films was studied by X-ray diffraction (XRD) and conversion electron Mossbauer spectroscopy (CEMS) techniques. The results revealed a transformation from alpha-phase that exhibits a body-centered cubic structure (BCC) to gamma-phase that exhibits a face-centered cubic (FCC) due to annealing. In addition, the percentage of gamma-phase structure increased with the increase of annealing temperature. Annealing thin films increased the crystal size of both phases (alpha and gamma), however, the increase was nonlinear. The results also showed that phase transformation was produced by recrystallization of alpha and gamma crystals with a temporal evolution at each annealing temperature. The texture degree of thin films was investigated by XRD rocking curve method, while residual stress was evaluated using curvature method. (C) 2016 Elsevier B.V. All rights reserved.