To provide a check valve, in which a check valve cartridge for general purpose can be used, the cartridge is easily taken out by only detaching a cover, the cartridge can be installed while positioning it in an appropriate direction only by installing the cover to a body, maintenance work is easy, and the incorporated cartridge can form the optimal piping path in a control of a flow rate and pressure loss.

In the check valve 4, the check valve cartridge 16 is housed from an opening part 10 of a valve body 8, and a cover body 13 is screwed into the opening part 10. The check valve cartridge 16 is pulled out from or inserted into the opening part 10 through a cartridge retaining tool 19, and the check valve cartridge 16 is detached from the opening part 10 by rotating operation of the cover body 13 while the cartridge retaining tool 19 is rotatably engaged with the cover body 13.