Micro mirrors connected in series are fabricated and studied for investigating loss mechanism of rotation hinge. Three identical mirrors (center-mirror and side-mirrors) are connected by torsion bars but the torsion bars of the center-mirror are not connected to supporting points of substrate. The other sides of torsion bars of the side-mirrors are fixed to the supporting points of substrate. Since the motions of the series-mirrors are identical to a single mirror in a specific rotational mode, the loss by the supporting points is estimated by comparing their Q factors in vacuum. The Q factor of the series-mirrors is higher by about two orders than that of the single mirror. The energy loss by the supporting points is estimated. The operation voltage of the comb-drive mirror under the resonant condition in vacuum can be decreased by suppressing the loss by the supporting points although the air friction loss is dominant.