Artificial structures such as stairs and bumps in roads are critical features that robotic platforms must overcome. Many robotic platforms have been developed for climbing stairs and for overcoming obstacles. However, the agility and maneuverability of the robotic platforms are not yet satisfactory. We propose a new field robot platform design that can climb various sizes of stairs as fast as human beings. The locomotion of the robotic platform is similar to the flipping (or tumbling) locomotion of humans, so we name the robot "FlipBot." The main body is composed of a tread-wheel mechanism. A supporting leg performs flipping locomotion during stair climbing while the tread-wheel generates the driving force on flat surfaces. Design parameters are optimized using the Taguchi methodology for stable climbing on various sizes of stairs based on kinematic relations. The assembled robot prototype can climb three different sizes of stairs around 1 step per second, which is generally as fast as human walking. We expect the proposed robot platform to be applied to inspection and service robotic applications in indoor environments.