In this study, the motion of an inverted pendulum mobile platform is extended to omnidirectional motion. omnidirectional motion is implemented by a drive unit constructed from paired mecanum wheels. The mechanism of the omnidirectional drive unit replaces the two parallel wheels of the inverted pendulum mobile platform and extends its motion to an omnidirectional motion. The mechanism of the omnidirectional drive unit and the control system are described. The control system is also extended to integrate the additional lateral motion into the two-parallel-wheel-type inverted pendulum control and performs path following control of the in-plane motion with complete three degrees of freedom. A simple additional control method is presented for the trajectory following control of the system that has unstable degrees of freedom. The ability of the system is demonstrated through an experiment of a trajectory following task. The experimental results indicate the omnidirectional motion ability of the mobile platform with auto balance and demonstrate the appropriate control method.