A wind-tunnel system for spinning body has been proposed to measure hydrodynamic forces acting on the body. In the proposed system, the body is suspended and rotated by electromagnets. The forces are measured from the control signal for suspension. An experimental apparatus was developed which has eight electromagnets around a wind-tunnel and an differential-type optical displacement sensor for detecting the three-dimensional positions of the body. Stable suspension, three-dimensional positioning and rotation of the body were achieved. This paper reports the measurement of the hydrodynamic force acting on the spinning body.