To restrict the occurrence of dry up of a fishpass by eliminating the runoff of river water than necessary by providing a rubber weir which is raised by controlling the inner pressure at the inlet portion of running water in fishpass and a partition wall constituted with a rubber bag body for varying the height by controlling the inner pressure in the middle of the fishpass in the longitudinal direction.

A raised type mini-rubber weir 3 installed to a concrete surface at the inlet of running water in a fishpass 1 changes its height by the internal pressure control by supply and exhaust air from a compressor. Also, a partition wall 4 consisting of a rubber bag body provided in the middle of the longitudinal fishpass 1 has an air chamber 4c made between a rubber sheet 4b adhered to the bottom of a water channel 2 and an airtight-sealed air chamber 4c, and the height of the partition wall can be changed by expanding and shrinking the rubber sheet 4a by the inner pressure control in the air chamber 4c by the supply and exhaust air from a compressor. In this way, the height of the rubber weir is made smaller thereby maintaining the function of the fishpass and the amount of water volume from the rubber weir can be controlled.