A mobile node for communicating through a mobile network (N1; N2), comprising: a first network device (11-1...11-n) to interface with a first network and to establish a connection to the first network; a second network device (11-1...11-n) to interface with a second network; a network quality monitor to monitor a quality of the first network based on at least one of an intensity and a radio bandwidth of a radio wave received by the first network device (11-1...11-n), wherein the network quality monitor includes a lowering threshold value and an abrupt degrade threshold value for detecting a lower quality of the radio wave; a hand-over controller to transmit a care of address to an address registering destination in response to a hand-over request from the network quality monitor, to change a route, used for upward transmitting packets and pointing to the first network device (11-1...11-n), to point to the second network device (11-1...11-n), and to switch the connection to the second network after a network controller receives a response indicating an update of the care of address in the address registering destination; and the network controller to receive the response, and to keep receiving packets from the first network before the connection is switched by the hand-over controller; wherein the network quality monitor is configured to recognize that the quality of the first network becomes lower and output a hand-over request to the hand-over controller when the quality of the first network is continuously lower than the lowering threshold value for a certain length of time; and wherein the network quality monitor is configured to recognize that the quality of the first network becomes lower and promptly output a hand-over request to the hand-over controller when the quality of the first network is lower than the abrupt degrade threshold value. a first network device (11-1...11-n) to interface with a first network and to establish a connection to the first network; a second network device (11-1...11-n) to interface with a second network; a network quality monitor to monitor a quality of the first network based on at least one of an intensity and a radio bandwidth of a radio wave received by the first network device (11-1...11-n), wherein the network quality monitor includes a lowering threshold value and an abrupt degrade threshold value for detecting a lower quality of the radio wave; a hand-over controller to transmit a care of address to an address registering destination in response to a hand-over request from the network quality monitor, to change a route, used for upward transmitting packets and pointing to the first network device (11-1...11-n), to point to the second network device (11-1...11-n), and to switch the connection to the second network after a network controller receives a response indicating an update of the care of address in the address registering destination; and the network controller to receive the response, and to keep receiving packets from the first network before the connection is switched by the hand-over controller; wherein the network quality monitor is configured to recognize that the quality of the first network becomes lower and output a hand-over request to the hand-over controller when the quality of the first network is continuously lower than the lowering threshold value for a certain length of time; and wherein the network quality monitor is configured to recognize that the quality of the first network becomes lower and promptly output a hand-over request to the hand-over controller when the quality of the first network is lower than the abrupt degrade threshold value.