To provide an operation support system which dispenses with an exclusive worker for the operation control of clean water/sewage water treating facilities or the like and facilitates the effective use of maintenance information of supply makers.

This operation support system is a system for efficiently operating a number of clean water/sewage water treating facilities or the like which are dispersedly disposed all over the country, The operation informations of a plurality of the facilities 1 are gathered in an operation support organization 4 through a business communication means 41. The operation support organization 4 processes the operation information into prescribed operation support information. The operation support information is transmitted to an operation control organization 2 that controls the facilities through a communication means 42, preferably a wide area network such as the Internet.