Operation of the omnidirectional mobile robot is more difficult as compared with the operation of a general mobile robot that controls two degrees of freedom, because it is required to control three degrees of freedom. On this point of view, we have developed a new control device for omnidirectional mobile robot that can be operated by foot, not by hands. By operating with foot, operator can use his hands for another task. A sphere is used as the device operated by the foot. By rotating the sphere in each axis direction, it is possible to control robot motion that has three degrees of freedom, a velocity vector of the robot and an angular velocity around the body.