A portal site for serving data monitored and observed, which can not only act for monitoring and observing services, instead of a facility owner, but also process the data into economically valuable data with the use of the result of monitoring and observation, is connected to a computer network so as to gather sequential data which is observed in time series by a not less than one sensor as to an operation running condition of a facility belonging the facility owner, and event data monitored invariantly, and incorporates a function of obtaining a data disclosure profile for designating a degree of disclosure of the data, from the facility owner, and a function of onerously serving an item of secondary data obtained by processing the data in a range satisfying the data disclosure profile, to a data user different from the facility owner.