Recently we have found that phase modulation atomic force microscopy (PM-AFM) has higher force sensitivity than amplitude modulation AFM (AM-AFM). The Q-control technique which is often utilized in AM-AFM allows to increase the effective Q-factor of the cantilever. In this study, we utilize the technique to PM-AFM and investigate the force sensitivity with and without the technique theoretically as well as experimentally. We show that the force sensitivity in PM-AFM is highly improved by the Q-control technique.