The laser nanosecond pulse heating of a steel surface has been considered. The temperature and stress fields during the heating pulse have been computed and the entropy change due to temperature and stress fields are derived and predicted. In the simulation, a laser pulse with a Gaussian energy distribution and with an intensity which varies exponentially with time is applied to the workpiece surface. It is found that the thermal stress field does not follow the temperature distribution inside the substrate material and thermal stress components in the region close to the symmetry axis are compressive. The entropy change due to the temperature field follows the temperature distribution and the magnitude of the entropy change due to the temperature field is considerably higher than that of the stress field.