In order to identify the distribution ratio of fish amount in each part of the main net area of set-net, experimental operations were conducted in four different sites of set-net fishing ground Chiba, Iwate, Ishikawa and Kanagawa prefectures. Each set-net of various size and shape has the non-return device of slope or funnel net, which defines the front part against the rear part of final stage for the hauling procedure. Distribution ratio of fish amount estimated as 20：80 on the small set-net in Tateyama Bay, Chiba prefecture, 31：69 for chum salmon Oncorhynchus keta on the small set-net in Otsuchi Bay, Iwate prefecture, 10：90 for sardine Sardinops melanostictus on the small set-net in Kanazawa area, Ishikawa prefecture, 27：73 on the large set-net in Hiratsuka area, Kanagawa prefecture. Fish density calculated from net volume and average fish amount in each set-net showed the higher value in the rear part of non-return device. The results suggest the reasonable performance of the non-returning function in the present gear designing, while farther modifications of fishing gear and methods are required from the view points of minimizing the catch loss in the front part of non-return devices.