This study attempted to show the diversity of fish caught by set net fishing on Futaoi-jima island, Japan by the taxonomic diversity (Δ+). Futaoi-jima island is located in Japan Sea in the western part of Shimonoseki, Yamaguchi Prefecture (lat. 34˚06' 13.5” N. and long. 130˚47’ 12.5” E). We read the fish species for each day stated in the catch slips in 2002 (No. operations: 249 days) and 2003 (241 days) and in 2012 (242 days) and 2013 (234 days), ten yeas after, and prepared a landed database. The numbers of species caught for four research years were 80, 79, 82, and 82, respectively. Diversity indices of fishes caught, as measured by Δ+, were 0.70, 0.71, 0.68, and 0.69, respectively.