Jiun Masuda (1883-1947) was a bridge designer representing Japan who played an active part in the Showa period of prewar days from the end of Taisho period (1920th-1930th). However, few documents remain from that time, but Masuda has been known only to a small group of specialists. In Fall 2002, it became clear that many reports and drawings for bridges that Masuda designed are saved in the Public Works Research Institute. In this paper, the achievements of Masuda were reviewed through these new documents and the actual bridges he designed. The research clarified that besides the well known bridges, Masuda had designed about 20 more bridges, subway stations, docks, quay walls etc. Moreover, it was revealed that he worked with very capable staff, designed the bridge of a variety of structure types, etc. Finally, the future application of these documents was discussed.