In order to clarify flow around a circular cylinder set normal to a plane wake of an upstream circular cylinder of the same diameter, a windtunnel experiment and an open water-channel experiment have been performed at Reynolds-numbers ( based on the diameter of the cylinder and the main velocity ) of 2.9×104 and 680, respectively. Surface-flow patterns of the downstream cylinder and flow patterns around the two cylinders were visualized respectively by the oilfilm and the hydrogen bubble methods. The flow patterns were found to be strongly dependent on the ratio of the distance between two cylinders to the diameter; they can be classified approximately into 3 patterns depending on the ratio. Time-mean and fluctuating pressures on the surface of the downstream cylinder were also measured and presented in the form of isoplethes.