The purpose of this study is to investigate the fatigue strength in accordance with back plate of butt welded specimens. Fatigue life of butt welded specimens was presented for determining the effect of back plates in terms of fatigue strength. As a results, fatigue strength of butt welded specimens with steel back plate show a decrease as compared against the butt welded specimens with ceramic back plate. Compared with the fatigue strength with respect to the existence of steel back plate, the specimens without back plate were much higher than the specimens with back plate.