A method for authenticating a user of a telematics terminal for a vehicle comprising: requesting, by the telematics terminal, a first telematics service from an information providing center through a mobile communication network upon receiving a request for the first telematics service from a user; receiving, by the telematics terminal, a first authentication request from the information providing center; storing (S13A), by the telematics terminal, a first user authentication information inputted by the user and transmitting in response the first user authentication information to the information providing center to receive the first telematics service; receiving, by the telematics terminal, the first telematics service from the information providing center, if the first user authentication information is valid; requesting, by the telematics terminal, a second telematics service from the information providing center upon receiving a request for the second telematics service from the user before the telematics terminal is turned off; receiving, by the telematics terminal, a second authentication request from the information providing center; transmitting, by the telematics terminal, in response the stored first user authentication information to the information providing center to receive the second telematics service; receiving, by the telematics terminal, a re-authentication request from the information providing center when the transmitted first user authentication information is not valid for the second telematics service; and in response to receiving the re-authentication request, requesting (S51, S71), by the telematics terminal, and receiving a second user authentication information from the user; and if the received second user authentication information is identical to the stored first user authentication information, transmitting, by the telematics terminal, the second user authentication information to the information providing center to receive the second telematics service, if the received second user authentication information is not identical to the stored first user authentication information, transmitting (S56, S77), by the telemetics terminal, a failure message to a communication device other than the telematics terminal, the communication device previously designated by the user of the telematics terminal. requesting, by the telematics terminal, a first telematics service from an information providing center through a mobile communication network upon receiving a request for the first telematics service from a user; receiving, by the telematics terminal, a first authentication request from the information providing center; storing (S13A), by the telematics terminal, a first user authentication information inputted by the user and transmitting in response the first user authentication information to the information providing center to receive the first telematics service; receiving, by the telematics terminal, the first telematics service from the information providing center, if the first user authentication information is valid; requesting, by the telematics terminal, a second telematics service from the information providing center upon receiving a request for the second telematics service from the user before the telematics terminal is turned off; receiving, by the telematics terminal, a second authentication request from the information providing center; transmitting, by the telematics terminal, in response the stored first user authentication information to the information providing center to receive the second telematics service; receiving, by the telematics terminal, a re-authentication request from the information providing center when the transmitted first user authentication information is not valid for the second telematics service; and in response to receiving the re-authentication request, requesting (S51, S71), by the telematics terminal, and receiving a second user authentication information from the user; and if the received second user authentication information is identical to the stored first user authentication information, transmitting, by the telematics terminal, the second user authentication information to the information providing center to receive the second telematics service, if the received second user authentication information is not identical to the stored first user authentication information, transmitting (S56, S77), by the telemetics terminal, a failure message to a communication device other than the telematics terminal, the communication device previously designated by the user of the telematics terminal.