To make hydraulic pressure mean at low cost by providing a rotary driving part and a rotary pressure part coaxially on a rotary shaft halfway in flows of water of different systems, and driving and rotating the rotary pressure part with the driving force of the rotary driving part according to the differential pressure between both the flows of water.

A Pelton wheel type rotary driving part A which is rotated by a flow of running water to generate a rotary driving force and a volute pump type rotary pressure part B are provided one over the other coaxially with the vertical rotary shaft 1. In this case, the rotary driving part A is coupled coaxially with the rotary pressure part B, so when the pressure of the water flow to the rotary driving part A is high, the rotary driving part A is forcibly rotated with its differential pressure. Then when the rotary driving part A rotates, the rotary pressure part B is rotated with its turning force and the flow of water flowing in with low pressure is pressed by the rotary pressure part B to increase the pressure. Further, the rotary driving part A which is driven to rotate so that the pressure is increased by the rotary pressure part B loses rotary energy because of its reaction force, so that the hydraulic pressure decreases.