The forming limit diagram (FLD) is one of useful parameters for evaluating the formability of sheet metal, and has been currently used in the development of forming processes of autobody panels. Also FLD plays an important role for the prediction of fracture in the analyses by numerical forming simulation. In this paper the influencing factors on FLD were examined experimentally. The experimental results of FLD depend on the experimental conditions such as tool shape and dimension, lubricant, gauge length and measuring preciseness. The effect of straining path on FLD is seemed large, but it is complicated to obtain FLD in complex straining paths experimentally. For efficient application of FLD in tool design and making, and stamping shops, there are still remained some problems to be solved.