Variable thickness plates are commonly used as structural members in the majority of industrial sectors. Previous fracture mechanics researches on variable thickness plates were limited to mode I loading cases. In practice, however, cracks are usually located inclined to the loading direction. In this respect, combined mode(mode I/II) stress intensity factors $K_{I}$ and $K_{II}$ at the crack tip for a variable thickness plate were obtained by 3-dimensional finite element analysis. Variable thickness plates containing a slant edge crack were chosen. The parameters used in this study were dimensionless crack $length{lambda}$, slant $angle{alpha}$, thickness $ratio{eta}$ and width ratio{omega}$</TEX>. Stress intensity factors were calculated by crack opening displacement(COD) and crack sliding displacement(CSD)method proposed by Ingraffea and Manu.