To provide an investigation method of a transport stream packet in which occupancy of a processor is reduced.

A start code prefix detection unit 104 determines whether or no there is a start code prefix from a transport stream packet according to a multiplexed stream. A three-byte state detection unit 105 detects the state of a byte sequence of three-byte from the backmost of the transport stream packet. A notification unit 106 notifies the determination results from the start code prefix detection unit 104, and the state of a byte sequence of three-byte extracted by the three-byte state detection unit 105, as the information of whether or not the start code of the transport stream is searched, to a stream analysis unit 103 which is driven by a processor.