To easily stop water after removing a storage pump of a deep well arranged in a pressing water layer.

A balloon stopper frame 11 is waterightly fixed along the inner periphery in the vicinity of an upper end part of a drain pipe 10, a water stop balloon 12 formed of an expansible raw material is inserted into the drain pipe 10 through the balloon stopper frame 11 in a contracted state, and air is sent into the water stop balloon 12 via an air injection hose 13 to be expanded. The water stop balloon 12 also rises according to an increase in pressing water quantity in the drain pipe 10, and when reaching the balloon stopper frame 11, the rise is restricted by the balloon stopper frame 11, but since the water stop balloon 12 tries to rise, the water stop balloon 12 is put in a state of being pressed to the balloon stopper frame 11 side, so that the water stop balloon 12 is put in a state of blocking up an opening part of the balloon stopper frame 11, that is, water is stopped.