To the forming of curved shells of ships, the line heating method is extensively applied. However, the line heating method is not suitable for automatic operation. The authors investigated a new system of plate bending, which is composed of a universal press with multiple piston heads. The universal press with multiple piston heads is quite suitable for numerically controled operation. Yet, there exist many problems which must be solved before the universal press is in practical use. In the paper, the authors conducted experimental investigation of plate bending by small press with a solid head (10 ton) and large universal press with multiple piston heads (500 ton). Various informations are obtained on the reproduceability of the results, the fairness of curved plate after bending, the amount of spring back after bending, the effect of pitch of multiple piston heads, etc. The authors also carried out theoretical investigations into the deformation of plates and proposed valuable empirical formulae. In the next paper, the authors will discuss the results of investigation into the various problems which arises from the numerically controled operation of the universal press with multiple piston heads.