The fuel injector is a pa.1 that controls the fuel supply of automotive engine. The housing of the fuel injector supports the rod, the needle valve and the solenoid. In this study, the rigid-plastic FE-analysis by using the design of experiments (DOE) and the response surface methodology (RSM) has been performed to produce the product reducing the under-fill and the maximum effective strain. From the results of DOE, the stem of counter punch and the face angle of punch at the $1^{st}$ process, and the stem of punch at the $2^{nd}$ process were determined as the significant design variables far each response such as the upper under-fill, lower under-fill and the maximum effective strain. From the results of RSM, the optimal values of the design variables have been also determined by simultaneously considering the responses.