PURPOSE: To enable prevention of weft insertion troubles, by providing a small hole connecting primary and secondary ports on the electromagnetic driving valve for selective actuation of plural weft insertion nozzles to also fill wafer in nozzles being out of weft insertion.

CONSTITUTION: In a water jet loom having plural weft insertion nozzles, each weft-insertion-nozzle branch pipe is fitted with an electromagnetic driving valve for selectively operating said plural nozzles. Said electromagnetic driving valve is provided with a small hole connecting a primary port (inlet) and secondary port (outlet). Thus, nozzles being out of weft insertion also allows to be adequately filled with water for weft insertion, leading to prevention of weft insertion troubles without interfering with the freedom of weft insertion selection by on-off operation of each valve.