In stormy days, there are many accidents of pedestrians who are holding an umbrella. It can be said that the behavior of the umbrella in wind is a problem related to human safety. We measured the characteristics of unsteady aerodynamic force under air currents with stepwise change of velocity. The inclinations of the umbrella are fixed at 0 degree and (plus, minus) 45 degree. As a result, when the umbrella is inclined to the upwind, the aerodynamic force. On the contrary, when the umbrella is inclined to the downwind or perpendicular, direction of the resultant force suddenly changes.
