To provide a method for collecting intermediate path performance monitoring(IPPM) that relieves a load of a network monitor by collecting monitor information of logically identical paths, without being aware of a cross connect state of a path in a cross connect node.

In a network system including cross connection nodes 101-104, each node which is a component of the network has a function of reporting a path trace reception value specific to each logical path and an IPPM value for each path, reports the IPPM value and the path trace reception value for each path to a network monitor 113, which identifies paths logically identical, based on the identical path trace reception value and conducts collating processing of the IPPM values based thereon.