A mobile communication terminal adapted to be selectively resident in both a first mobile communication network where a data communication and a voice call can be performed and a second mobile communication network where data communication faster than in the first mobile communication network can be performed, the mobile communication terminal being set to be preferentially resident in the second mobile communication network in a case where the data communication is performed and being adapted to switch the mobile communication network so as to be resident in the first mobile communication network in a case where the voice call is performed, the mobile communication terminal comprising receiving means adapted for receiving network information representing a function of the second mobile communication network from the second mobile communication network and location registration request means adapted for making a request for a location registration in each of the mobile communication networks to the second mobile communication network, wherein the receiving means is adapted for receiving, as the network information, a location registration response representing a result of the location registration in the both mobile communication networks in response to the request for the location registration made by the location registration request means, characterized in that the mobile communication terminal further comprising: switching possibility determination means adapted for determining that, based on the network information received by the receiving means, whether or not the second mobile communication network is a switchable mobile communication network where the mobile communication terminal can switch the mobile communication network so as to be resident in the first mobile communication network in a case of receiving a calling of a voice call during being resident in the second mobile communication network; and first mobile communication network switching control means adapted for automatically performing the switching control of the mobile communication network for causing the mobile communication terminal to be resident in the first mobile communication network in a case where the switching possibility determination means determines that the second mobile communication network is not the switchable communication network, wherein the switching possibility determination means is adapted for determining whether or not the location registration only in the second mobile communication network of the both mobile communication networks is completed, based on the location registration response received by the receiving means, and determining that the second mobile communication network is not the switchable mobile communication network, in a case where the location registration response, which is received by the receiving means, represents that only the second mobile communication network of the both mobile communication networks completed the location registration. switching possibility determination means adapted for determining that, based on the network information received by the receiving means, whether or not the second mobile communication network is a switchable mobile communication network where the mobile communication terminal can switch the mobile communication network so as to be resident in the first mobile communication network in a case of receiving a calling of a voice call during being resident in the second mobile communication network; and first mobile communication network switching control means adapted for automatically performing the switching control of the mobile communication network for causing the mobile communication terminal to be resident in the first mobile communication network in a case where the switching possibility determination means determines that the second mobile communication network is not the switchable communication network, wherein the switching possibility determination means is adapted for determining whether or not the location registration only in the second mobile communication network of the both mobile communication networks is completed, based on the location registration response received by the receiving means, and determining that the second mobile communication network is not the switchable mobile communication network, in a case where the location registration response, which is received by the receiving means, represents that only the second mobile communication network of the both mobile communication networks completed the location registration.