To provide an in-pipe aeration device discharging as rich dissolved oxygen water in a pipe or the like in the halfway of forced feed before releasing in the water to a necessary place in the water, also capable of aeration of direct release in the water as in the past, having a simple kind with also maintenance control easy at a low cost.

This in-pipe aeration device, using a pump (temporarily called [gas liquid pump]) forcedly feeding gas liquid together by the same pipe, providing an irregular part in a pipe inner wall part in the halfway of forced feed or a gas liquid contact spoil material in the pipe inside, making gas liquid pass together in alternate or mixed condition, enhancing an aeration effect in the forced feed pipe, after generating rich dissolved oxygen water, releasing it in the water, providing a gas liquid separator in the forced feed pipe as necessary to separate the gas liquid, singly forcedly feeding either one of gas or liquid in the water, and using the pump in a necessary place of water bottom region or the like in the case of liquid only and in aeration of air bubble release in the water in the case of gas only similar to in the past, is used for purification or the like of water quality in the various kinds.