Ishii Kikujiro was one of the great Japanese diplomats in the first half of 20th century. He was famous for his contribution to the development of the League of Nations. However, he has been often remembered as a diplomat without the vision because he agreed to the 4th Japan-Russo entente in 1916 even though it was against his will and by the compulsion of the grand old man, Yamagata Aritomo.This paper describes the track record of Ishii as a diplomat during World War 1 in order to efface his images as a diplomat without a vision.Firstly, we examine Ishii’s diplomatic behavior as Japanese ambassador to France (1912.7-1915.8). Ishii continued to be against the Franco–Japanese alliance agreement due to French government’s strong demands. On this matter, he corresponded with Foreign Minister Kato Takaaki who was pro English. However, in contrast to Kato, Ishii was enthusiastic for Japanese participation to the London Declaration concluded by England, France and Russia on the 5th of September 1914. This enthousiasm was because he prefered a multilateral alliance or cooperation.Secondly,we will examine Ishii’s diplomatic behavior as foreign minister (1915.10-1916.810). Ishii accepted the conclusion of the Russia-Japan alliance although he did not like the alliance . In this way, he was different from Yamagata Aritomo and Motono Ichiro who were pro russia. He did it only for maintaining the cooperation between the four states : that is Japan,England,France and Russia. He was fundamentally a multilateralist. But ,in those days ,he didn’t have a clear vision of the future world order that we know today.Thirdly,we will examine Ishii’s diplomatic behavior as Japanese ambassador to the United States (1917.8-1919.6) . During this period, he concluded the Ishii–Lansing agreement. This was the achievement of a network of multiple alliances and ententes which the Japanese government had sought for a longtime. But the important thing was that he learned the idea of liberalism and international justice from U.S. president Woodrow Wilson. From this knowledge, Ishii was be able to obtain a vision of the postwar international order on the basis of justice and prepared himself to play an active part at the League of Nations. In this regard, he was far ahead of any other Japanese statesman and diplomat of the period.