To provide a high precision delay measurement equal to or less than the unit of milliseconds suitable for a measuring method or the like to which high precision is required for measuring delay time in a distributed computer network environment or the like.

A time source S is acquired from a time server 101, a frame synchronizing signal FS is detected from a synchronous media 102, time is managed by using them, a time stamp generated on the basis of this managed time is distributed to the transmitting side and receiving side of an asynchronous transmission network, a packet P containing a time stamp TS1 distributed to the transmitting side is transferred through the asynchronous transmission network to the receiving side, the time stamp is extracted from this packet, the difference between this extracted time stamp and a time stamp TS2 distributed to the receiving side is calculated and the transmission delay time of the network is measured from this difference.