A paddy field water level regulating device 6 installed between a water pipe buried along a farm road 43 and a farming plot 42, the device consisting of a cylindrical feed and drain basin 60 with a closed bottom, having a farming plot feed and drain port 61 communicating with the farming plot 42; a water inflow and drain section located in the geed and drain basin 60 near the bottom thereof and connected to the water pipe; a drain valve located in the water inflow and drain section; and a height-adjustable water level regulating weir 65 located in and water inflow and drain section.