Experiments on the fluid friction of a rotating disc which has protuberances on its surface are performed. The author arranged blades radially or concentrically on the disc and on the vessel, and carried out experiments on same combinations of the disc and vessel which have blades or smooth surfaces. The main results obtained are as follows : 1) The relation between C_f and R₆ can be expressed by C_f=α·R₆^-0.1575. 2) The value of α increases first rapidly with the number of blades and then gradually approaches to a minimum value. 3) The shapes of blades (logarithmic and straight) have little influences on C_f for small clearance. 4) The increment value of C_f induced by the blades on the disc is nearly twice as large as the value by the blades on the vessel. 5) The boss ratio smaller than 0.5 has little influences on the value of C_f.