For automatization of the line heating work that is a basic technology in making curved surfaces of ships it needs to evaluate transverse shrinkage generated by triangle heating quantitatively. In this paper, techniques were examined in triangle heating tests and an estimation method using FEM analyses were developed in the first place. Secondly numerical simulations of triangle heating discussed effects of line heating factors that were curvature radius in the transverse direction, water-cooling and heating length. It was concluded that curvature radius in the transverse direction had least effect in transverse shrinkage and water cooling following the heating touch led to efficient shrinkage. And as the parameter value of heat input in the panel end part was increasing with varying travel speed, transverse shrinkage generated lager, so that it was approximately proportional to the parameter value. The maximum shrinkage was achieved when heating length was from 0.3 to 0.4 times as long as plate width.