In Japan, four different welding methods have been applied for rail welding. One is the "Enclosed Arc Welding (EAW)" method. The application ratio of this method is approximately 10%, as it can be applied at the in-track site. However, the EAW requires special skills for welding. Therefore, the quality of weld largely depends on the operator's skill, and discontinuities are often observed by the ultrasonic inspection. In this paper, we propose new criteria of soundness evaluation for the EAW through various tests concerning the soundness of EAW.