The present study deals with an application of the finite element method to the sensitivity analysis of processing parameters for laser surface hardening treatment. Computing the sensitivity of temperature distributions to changes in processing parameters allows one to determine the more effective input parameters for laser surface hardening treatment. The interesting processing parameters are taken as the characteristic beam radius (r b and the laser scan velocity (v). A state equation governing the heat flow in laser surface treatment is analyzed using a three-dimensional finite element method. The response sensitivities of the temperature T versus r b and v distributions were obtained using a direct differentiation method. To verify the numerical analysis results, hardened layer dimensions of the numerical analysis are compared with experimental results.