Visual line-transect surveys for the finless porpoise (Neaphocaena phocaenoides) were conducted in the offshore of the west coast of Korea (WCOK) from 18 April to 17 May 2001 (34`18` to 37°18`N, 123`00` to 126`00`E), and in the inshore of the west coast of Korea (WCIK) from 29 July to 2 August 2003 (35`17` to 36°17`N, 126`00` to 126°25`E). A total of transect supey efforts werf 810.27 n.m. in 2001 and 216.09 n.m. in 2003, which cover a survey areas of 23,012 n.m. and 1,550 n.m. , respectively. There were 76 and 24 sightings for the finless porpoise during the surveys in the WCOK (2001) and the WCIK (2003), respectively. More than 80% of the finless porpoise occurred near the coast within 15 n.m. from the land. Porpoise were observed mainly in a depth range from 20 to 50 m (78%). Few porpoise were observed in a depth shallower than 10 m or deeper than 60 m. The hazard-rate model, truncated at the largest 5% distance, showed the best fitting from the frequency distribution of perpendicular distance of the finless porpoise sighted from the trackline in the WCOK (2001), while the uniform model showed the best fitting from in the WCIK (2003). Abundance of finless porpoises were estimated to be 58,650 individuals (95% CI=34,961-98,389) in the WCOK (2001) and 1,571 individuals (95% CI=881-2,800) in the WCIK (2003), respectively.