To swing liquid flow by force of liquid flow by incorporating an impeller plate restricting means and an impeller plate restriction releasing means with each other, and inversion swinging a casing at a prescribed angle.

An impeller plate 2a is unrotatably restricted at a position rotated by 45° from a horizontal position in anticlockwise direction, and an impeller plate 2b is unrotatably restricted at a horizontal position. Water flow (a) is rotated by reaction bent in a right direction, and a pump casing 1 is rotated in a clockwise direction around an axis L. Water flow (a) is also swung in a clockwise direction. The impeller plate 2a is fixed to a horizontal position, and the impeller plate 2b is fixed to a position rotated by 45° from the horizontal position in a clockwise direction. The water flow (a) is bent in a left side by the impeller plate 2b, and the pump casing 1 is rotated around the axis L in a counter clockwise direction. The water flow (a) is also swung in the counterclockwise direction. The pump casing 1 and the water flow (a) are swung in right and left directions by alternate repeat.