A stream data generating method for a computer system for generating stream data having time information applied thereto in a time series order and processing the generated stream data on the basis of a registered query. The computer system includes a storage for storing therein query information indicative of a plurality of sorts of constituent elements forming stream data corresponding to the query on the basis of the query and a stream definition indicative of the plurality of constituent elements, a data generator for generating and transmitting stream data; and a stream data processor for processing the stream data transmitted from the data generator. The data generator a less quantity of stream data to be transmitted to the stream data processor on the basis of the query information.