To provide a water stop machine capable of automatically stopping an intake into a paddy field and convenient to intake water from an agricultural water path to the paddy field, etc.

This water stop machine is used for stopping water in a paddy field by automatically lowering a valve when a water level attains a prescribed level according to a monitored result of a water level detector. Breadth controlling boards 18 are fitted to right and left side positions of an upper board 14a and a lower board 15a of a body frame. Each of the breadth respectively controlling the boards 18 can pulling out a board outward by only loosening a screw 145 within a range a long hole 181 is formed, then the breadth of the body frame.