Abstract: A method for a path trace check reducing a load on a computer, raising the speed of the check, and easily enabling an increase of nodes to be added. On a sender side, a first computer simply generates path trace data, adds a specific code CR to this, multiplexes this to the transmission data, then transmits the same to a transmission line. On a receiver side, a second computer simply generates an expected value of the path trace data, autonomously compares this expected value and the actual path trace data extracted from the received transmission data by using the specific code, and determines coincidence of the two.