An impact energy absorbing propeller shaft may include a collet integrally and rotatably inserted between a spline portion formed on an outer circumferential surface of a front shaft and a spline portion formed on an inner circumferential surface of a rear shaft, and an O-ring fitted with an outer circumferential surface of a rear end portion of the collet, fixedly holding a rear end portion of the front shaft, and fixedly supporting the collet inside the rear shaft.