A testing device and method for determining the coefficient of restitution of a rebounding object, such as a ball, by comparison of the bounce periods of successive bounces of the ball. The ball is dropped onto the reaction plate from which it is permitted to rebound at least three times. A transducer such as a microphone is mounted near the reaction plate to detect the impacts on the reaction plate. An electronic circuit times the interval or bounce period between impacts, stores the bounce periods for comparison. The coefficient of restitution for the rebounded object is determined by comparing a subsequent bounce interval to a preceding bounce period as a ratio. The coefficient of restitution so determined is displayed on an LCD display.