An on-vehicle communication system in which a switching hub capable of relay of communication and path selection according to a destination of communication is provided at each of a plurality of positions, for which branching off is possible, on a wire harness including a trunk line (76A-76E), wherein each trunk line (76A-76E) includes a communication line of the Ethernet standard; wherein each of a plurality of the switching hubs comprises: a failure detection part that detects occurrence of a failure, namely disconnection or decrease in communication quality and specifies a position of the occurrence of the failure; a routing map; and a path control part that controls rewriting of the routing map; and wherein the trunk line (76A-76E) of the communication line is formed in a state where it is possible to selectively use a plurality of types of paths physically or logically; the on-vehicle communication system characterized in that: the routing map holds a plurality of types of path information for selecting an alternative path determined in advance in correspondence to presence or absence of a failure and each failure position; when the failure detection part of any switching hub detects failure occurrence, the path control part in the switching hub whose failure detection part detects the failure occurrence transmits information indicating the occurrence of the failure and the position of the occurrence of the failure to any other of the plurality of switching hubs to change a path; and when the failure detection part of any switching hub receives the information indicating the occurrence of the failure and the position of the occurrence of the failure from any of the other switching hubs, at least the routing map in the switching hub whose failure detection part receives the information is rewritten in accordance with the position of the occurrence of the failure. a failure detection part that detects occurrence of a failure, namely disconnection or decrease in communication quality and specifies a position of the occurrence of the failure; a routing map; and a path control part that controls rewriting of the routing map; and wherein the trunk line (76A-76E) of the communication line is formed in a state where it is possible to selectively use a plurality of types of paths physically or logically; the on-vehicle communication system characterized in that: the routing map holds a plurality of types of path information for selecting an alternative path determined in advance in correspondence to presence or absence of a failure and each failure position; when the failure detection part of any switching hub detects failure occurrence, the path control part in the switching hub whose failure detection part detects the failure occurrence transmits information indicating the occurrence of the failure and the position of the occurrence of the failure to any other of the plurality of switching hubs to change a path; and when the failure detection part of any switching hub receives the information indicating the occurrence of the failure and the position of the occurrence of the failure from any of the other switching hubs, at least the routing map in the switching hub whose failure detection part receives the information is rewritten in accordance with the position of the occurrence of the failure. the routing map holds a plurality of types of path information for selecting an alternative path determined in advance in correspondence to presence or absence of a failure and each failure position; when the failure detection part of any switching hub detects failure occurrence, the path control part in the switching hub whose failure detection part detects the failure occurrence transmits information indicating the occurrence of the failure and the position of the occurrence of the failure to any other of the plurality of switching hubs to change a path; and when the failure detection part of any switching hub receives the information indicating the occurrence of the failure and the position of the occurrence of the failure from any of the other switching hubs, at least the routing map in the switching hub whose failure detection part receives the information is rewritten in accordance with the position of the occurrence of the failure.