We present a real-time simulation method for muscles which are actuated by skeletal structure based on anatomical properties of the muscles. Muscles are designed by their two endpoints attached to either bones or other muscles and their volume are preserved approximately during the deformation. Skin deformation animation is obtained by a simple skinning due to the muscle deformation. We present also the performance data for a human-like multi-linked character which has bones, muscles, and skin. According to our experimental result, we can get skin deformation animation with a few tens of muscles in real-time. The method proposed in this paper can be applied to obtain skin deformation animation for multi-linked characters appear frequently in real-time environments such as games.