— A new 3D biped prototype with small DOF, SKIPPER, was developed. As an important component of a running controller for this robot, an aerial posture controller is presented. This is the extended version of planar running controller, which was previously developed for a passive one-legged hopping robot, and plays important roll for orbital stabilization at the lowest control layer. The controller stabilizes three output functions defiened as lareral leveling, holonomic constraint of pitch dynamics, and linearization of swing leg dynamics. Simulation results show that the robot achieves desired posture control for wide sets of initial conditions, naturally utilizing its compensator around yaw axis. In this paper, after describing the 3D biped model and its basic running control strategy, the details of the aerial posture controller are presented, as well as the simulation results.