To provide a butterfly valve with water filling function for supplying fluid during water filling to a pipe.

The butterfly valve with water filling function includes a valve seal part 20 formed on the inner periphery of a valve box 1 and a valve body 10 which comes into sliding contact with the valve seal part 20 in the full closure state via a valve rod 11, wherein, while a circumferential part 10a of the valve body 10 rotates by a prescribed angle, a slidable extension part 22 is extended from a valve seal part 20 and filling water is caused to flow through a water-passable pore 25 formed on the extension part 22 by rotation of the valve body 10.