A mobile terminal device that forms an adhoc network comprises a clustering section that identifies the ID and state of a mobile terminal device that is adjacent to the mobile terminal device itself by exchanging a Hello packet (containing the ID and state of the mobile terminal device itself) with the other mobile terminal device and which, based on the state of the adjacent mobile terminal device and the state of the mobile terminal device itself, sets the state of the mobile terminal device itself as a cluster head, gateway, or member; a storage section that stores the ID and state of the adjacent mobile terminal device and the state of the mobile terminal device itself; a link information transmit/receive section which, when the state of the mobile terminal device itself is the cluster head, transmits link information containing the ID of the adjacent mobile terminal device and the ID of the mobile terminal device itself and receives link information from the other mobile terminal device; and a routing section that finds a route to any mobile terminal device on the basis of the link information thus transmitted and received.