本文主要追索第二次世界大戰前日本人辯護士古屋貞雄在日本、朝鮮、臺灣三地間的活動與軌跡，分析他在殖民地與社會政治運動中的定位，以及在跨境後所帶來的衝突、矛盾與融合。1889年古屋貞雄出生於日本山梨縣農家，明治大學法科在學時期即投入家鄉的農民運動，1920年考取辯護士資格，致力於日本勞農民運動以及法庭辯護活動，為戰前自由法曹團創始團員之一，被定位是人權派辯護士、抵抗法曹。1927年赴京城擔任朝鮮共產黨事件之辯護人，同年底勞農黨派遣古屋到臺灣擔任臺灣農民組合之顧問，因而舉家遷居至臺灣。1927年至1934年間擔任許多勞農事件與政治事件的民刑事訴訟之代理與辯護。在勞農運動中，古屋將在日本的運動抗爭手段帶入臺灣，對臺灣社會產生了一定啟蒙的效果。1935年荷蘭船朱諾號事件中，古屋一方面主張辯護士的獨立性，一方面卻支持日本軍部國權至上的見解，讓我們看到人權派辯護士的侷限與轉向的開始。中日戰爭爆發後，古屋從抵抗法曹完全轉向為擁護國權的臣民法曹。戰前的古屋擁有許多不同的面孔，對於殖民地勞農與社會運動的法庭支援應給與正面評價。但他對國家權力的抵抗仍是以體制內為前提，並未曾將自己定位是體制外的他者，在戰爭期間只能陷於天皇體制的泥沼中動彈不得。

This paper traces the trajectories and activities of Furuya Sadao, a Japanese lawyer, in Imperial Japan and Colonial Taiwan. It also analyzes his roles in socio-political movements in Colonial Taiwan, and the conflicts which he encountered after border-crossing. Born in 1889 to a farmer family in Yamanashi, Furuya had participated in peasant movements during his studies at the Law School of Meiji University. After obtaining his lawyer license in 1920, he became committed to the legal defense activities for labor and peasant movements. Furuya was also one of the founders of Japan Lawyers Association for Freedom (JLAF), and had been regarded as a human rights lawyer, while participating in political activities and joining the Labor-Farmer Party. He went to Seoul in Colonial Korea as a defender lawyer of the Korean Communist Party Incident in 1927. At the end of the same year, the Labor-Farmer Party dispatched Furuya to Colonial Taiwan as a consultant to Taiwan Peasants' Union. Therefore, he and his family moved to Taiwan. In Taiwan, social movements flourished in the second half of the 1920s. Furuya served as a lawyer for many labor or peasant cases and also some political ones between 1927 and 1934. In these cases, Furuya introduced strategies and techniques which had been used in Japan. His opinions and behaviors certainly brought enlightenment to Taiwan society. However, social movements became overheated and gradually lost mass support. In the Juno Incident of 1935, Furuya, on the one hand, advocated the independence of lawyers in the investigation of the Incident, while, on the other hand, supported the supremacy of state power. His dual and dubious stand revealed limitations and changes of his ideology. During the Second World War, Furuya was completely transformed from a human rights lawyer to one who upheld the state power. This paper analyzes the many and varied roles of Furuya before WWII. His efforts for supporting peasant and social movements in colonies merited recognition. Nevertheless, his resistance to state power was after all within the establishment. Owing to such weakness of his ideology, he could not escape from it being trapped in the imperial system during the war.