A transfer protocol conversion method and a protocol conversion equipment are disclosed in order to transmits TS packets for a CATV network, a DAVIC network or the like by use of IP packets for the Internet. In a network using TS packets, the transmission is made with an Internet protocol header stored in a private field of an adaptation field defined in the TS packet. An equipment for protocol conversion between a network using TS packets and an Internet forms an IP packet for the Internet by use of the header transferred by the private data. Further, lower 8 bits of the IP address of an IP packet and lower 8 bits of the PID value of a TS packet are made the same and upper 24 bits of the IP address are converted into a 5-bit value so that the converted 5-bit value is made to correspond to upper 5 bits of the PID value.