Diving behavior of an adult female northern elephant seal, Mirounga angustirostris, was recorded by a velocity meter and a time-depth recorder (TDR). The instruments were attached at Ano Nuevo in California in Feb. 1989. Velocity deta of northern elephant seal was recorded for the first time in this resarch. Mean descending distance was longer than mean ascending distance recorded by the velocity meter, and mean vertical descending rate was smaller than mean vertical ascending rate recorded by the TDR. These results suggest that ascent of the dive was more vertical than descent of the dive.