To provide a fluid-driven mill capable of improving conversion efficiency from wind power energy to electric power in a windmill, and used for reducing manufacturing cost associated with fan plates and a supporting rod because a long and strong supporting rod is required for supporting the fan plates in a large windmill.

This fluid-driven mill includes: a supporting member 2 including a vertical shaft part 21, a plurality of stoppers 24 and a lower seat part 23; and a plurality of vertical plate members 4 each having a drive surface 40, wherein each vertical plate member 4 is mounted to the supporting member 2 to be rotatable relative to the supporting member 2 about a corresponding rotational axis Y which is parallel to a central vertical axis X defined by the vertical shaft part 21 between a pushing position and a release position. The plurality of vertical plate members 4 are angularly displaced from each other and are disposed around the central vertical axis X. The plurality of stoppers 24 are disposed between an imaginary cylindrical plane formed by the rotational axis Y and the vertical shaft part 21.