Along with advances in virtual reality technologies, augmented biofeedback technique has been getting attention as a feasible tool for guiding motor skill acquisition. To supervise the optimal way of muscular activation in skillful piano playing, we developed a vibrotactile biofeedback device for noticing excessive muscular activities to a learner. A pilot experiment indicates that training with the vibrotactile biofeedback device can potentially inhibit involuntarily-exerted excessive muscular activation without deteriorating fine motor control during playing the piano.