To provide a finishing trowel supporting structure capable of forming a concrete floor surface excellent in flatness and aesthetic appearance in a rather short time and reducing the number of skilled workers in a floor surface finishing device having a propeller type rotating trowel and a finishing trowel.

The floor surface finishing device 1 comprises a leveling machine 5 having the propeller type rotating trowel 4 rotating while coming into contact with a floor surface 2 to be finished and the flat plate-like finishing trowel 8 disposed in a part of the outer peripheral area of the rotating surface of the rotating trowel 4 in the state thereof connected to the leveling machine 5. The finishing trowel 8 is supported so that a part of the finishing trowel 8 is brought into contact with the floor surface 2a to be finished after the rotating trowel 4 is passed in a contact state. The floor surface finishing device further comprises a mechanism for holding the finishing trowel 8 formed of a elastically deformable steel sheet in a tilted attitude having an elevation angle toward the rotating axis C of the rotating trowel 4, a mechanism liftably holding the finishing trowel 8 while holding the tilted attitude, and a weight 15 pressing the finishing trowel 8 against the floor surface 2a to be finished.