An object of the present invention is to provide an inside drum-type tire testing device, which can significantly improve operability and test precision, reliably has strength high enough to eliminate any concern about strength thereof, and has relatively small size and significantly small floor-occupied area. Specifically, the present invention provides a tire testing device, comprising: an inside drum-type cylindrical rotating drum 1; a fixed support member 2 for surrounding the rotating drum 1 from the outer peripheral side of the drum via rotation guide means 3; and a linear motor 4 provided between the rotating drum 1 and the fixed support member 2, for rotationally driving the rotating drum 1.