A robot used indoors is required to be light and small. Such a robot may generate a resonance phenomenon in a comparatively low frequency band. And it may generate oscillations when it is controlled. Therefore we need a way of control which doesn't generate oscillations or reduces the oscillations. This paper we treat a inverted pendulum with flexible joint as a model. We propose a control method for such a model. To design a control, we consider flexibility of joints. A purpose of paper is showing effectiveness of the proposed control method by simulations and experiments.