This paper aims to lower the operational force for bilateral control under time delay while guaranteeing stability. Bilateral teleoperation system enables humans to work in remote places. However, time delay on network impairs the stability and the performance. The conventional method has trade-off problem between stability and operationality. This paper introduces the concept of equilibrium acceleration, which includes both position and force information, and proposes a method to detect vibration based on the difference of equilibrium acceleration. As a result, the algorithm can be considered simply, and it is possible to stabilize only during vibration and improve the operationality in free motion. Since this paper does not focus on frequency, but vibration, damping control works only during vibration and the operational force can be reduced compared to the conventional method. The effectiveness of the proposed method is verified by simulations and experiments.