A concrete floor trowel machine, developed in the U.S in 1990's, consists of only two rotary trowels, and doesn't need any other mechanism for motion such as wheels. When the machine flattens a concrete floor with its rotary trowels, the machine can move in any direction by utilizing the unbalanced friction forces occurring between the rotary wheels and the floor when the trowels are tilted in appropriate directions. In order to automate the trowels machine, this paper proposed the self-propulsive concrete finishing trowel robot which has twin trowels. For the control of the robot, this paper discussed the following. Firstly, the dynamics model of the driving frictional force applied on each trowel from the floor is derived. Secondly, the relationship between the driving force for the robot and the control variable of the robot is derived. Finally, the basic motion of the robot are realized by using the obtained relationship. This paper figures out how the concrete floor finishing robot with tow trowels moves and will contribute to realizing it.