A device for providing a mobile Internet call service, comprising: a communication unit configured to perform communication for a mobile Internet call service; a storage unit configured to store a main call number list including at least one main call number and network address translation information for a call connection; and a control unit configured, when power of a terminal is turned on, - to send a signal requesting NAT information for a mobile Internet call of the main call number, - to receive and store NAT information for the mobile Internet call, - to generate a light weight session using the NAT information, and - to maintain the generated light weight session, wherein the control unit is further configured, when a mobile Internet call request is made for the main call number, to use the light weight session to perform a direct call connection to the main call number, wherein the control unit is further configured, when the number of main call numbers is greater than a predetermined number: - to measure a number of call connection attempts of main call numbers for a predetermined time, and - to designate a priority in descending order of the measured number of attempts, wherein the control unit is further configured to have the generation and maintenance of light weight session for only the main call numbers of a predetermined number based on the designated priority. a communication unit configured to perform communication for a mobile Internet call service; a storage unit configured to store a main call number list including at least one main call number and network address translation information for a call connection; and a control unit configured, when power of a terminal is turned on, - to send a signal requesting NAT information for a mobile Internet call of the main call number, - to receive and store NAT information for the mobile Internet call, - to generate a light weight session using the NAT information, and - to maintain the generated light weight session, - to send a signal requesting NAT information for a mobile Internet call of the main call number, - to receive and store NAT information for the mobile Internet call, - to generate a light weight session using the NAT information, and - to maintain the generated light weight session, wherein the control unit is further configured, when a mobile Internet call request is made for the main call number, to use the light weight session to perform a direct call connection to the main call number, wherein the control unit is further configured, when the number of main call numbers is greater than a predetermined number: - to measure a number of call connection attempts of main call numbers for a predetermined time, and - to designate a priority in descending order of the measured number of attempts, - to measure a number of call connection attempts of main call numbers for a predetermined time, and - to designate a priority in descending order of the measured number of attempts, wherein the control unit is further configured to have the generation and maintenance of light weight session for only the main call numbers of a predetermined number based on the designated priority.