This paper presents an effect of riblet shape on turbulent drag reduction. The experiment was carried out in an N.P.L.blow-down-type wind tunnel with a working section of 500mm×500mm×2000mm. In order to investigate the details of drag reduction for riblet shape, rib models of scaling up riblets were used in this experiment. The parameters were 5 kinds for the rib model and 7 kinds for the riblet model. The time-mean velocity and skin friction were measured by the Pitot and static pressure tubes and Preston tube respectively. The Reynolds stress was obtained using the data processing system connected to a hot wire anemometer. Consequently it was found that(i)the Reynolds stress and skin friction become smallest near the surface for the rib with the section of an equilateral triangle, and(ii)the drag reduction attains maximum for the riblet of V groove with nearly equilateral triangular section.