The resistance of a flow through co-axial cylinders of which the inner cylinder rotates is studied experimentally, when there are grooves peripherally on the inner cylinder or on the outer cylinder. Results obtained are as follows : (1) When the Reynolds number R₆ is larger than about 200, the value of resistance coefficient λ of grooved cylinder is much larger than that of non-grooved one, whether the inner cylinder rotates or not. (2) When rotating Reynolds number R_w is large, the value of λ increases with the increase of clearance. (3) When the pitch of grooves is constant, the value of λ increases with the increase of breadth of the grooves.