Size selectivity of net-pot of several mesh sizes for white-spotted conger eel Conger myriaster were estimated using the extended SELECT analysis method. Paired gear tests （net-pots of five mesh openings; 11.6, 13.6, 15.5, 18.1, and 21.0 mm versus net-pots covered with small mesh of 10.8 mm mesh opening as control gear） were carried out the total 20 times during October and early November in 1995 and 1996. The requirement to combine data of each time is constant fishing-effort ratio of the test gear to the control gear or no change in length frequencies. Because of significant difference in total length frequencies between the two years, data of each year were therefore not combined for mesh openings with different gear numbers were used in the two years, and then split parameters were estimated for each year. Selectivity curve of each mesh opening obtained in this study was attributed chiefly to mesh selectivity of the net, because it was quite similar to that estimated from the cover-net method in the previous study. However, the curve in this study has 50% retention length of slightly larger than the cover-net. This implies an effect of cover-net on behavior of conger eel passing through mesh of net-pot in the cover-net method.