Melting and vaporization phenomena during the laser drilling process are investigated in this paper. The locations of the solid-liquid and liquid-vapor interfaces were obtained by solving energy conservation equations at the interfaces. The dependence of saturation temperature on the back pressure is taken into account by using the Clausius/Clapeyron equation. The conduction heat loss to the solid is also included in the model and is solved by using an integral approximate method. The results show that the fraction of the heat lost through conduction to the solid is very small and its effect on the vaporization process is not significant. On the other hand, the conduction heat loss significantly reduces the thickness of the liquid layer, which becomes the recast layer after drilling.