The present invention provides a method for processing stream data and a system thereof capable of implementing general data processing including recursive processing with low latency. In the system for processing stream data, a single operator graph is prepared from operator trees of a plurality of queries, an execution order of the operators is determined so that execution of a streaming operator is progressed in one way from an input to an output, the ignition time of an external ignition operator that inputs data from the outside of the system and an internal ignition operator that time-limitedly generates data is monitored, and an operator execution control unit repeats processing that completes the processing in the operator graph at the time according to the determined operator execution order, assuming the operator of the earliest ignition time as a start point.