A character stream search system using an FSA for determining at a time whether or not a plurality of character streams as search objects exist in a search character stream which undergoes a search operation and which comprises a plurality of characters expressed with codes. In the system, a collation is conducted between the search character stream and a search object character. In a case where there exists a matched search object character as a result of the collation, a state transition is carried out of a predetermined state indicated by the FSA. In a case where there does not exist a matched search object character, a failure processing to effect a state transition to a transistion destination which is determined in association with the configuration of the FSA. The following processing is completed at a count which is a predetermined upper-limit value for each character undergone the search operation.