A method for transmitting authentication information of a service provided from a service providing server at a first device in a wireless communication system comprising a plurality of devices includes obtaining, from an authentication server, first access information using an authentication code obtained based on an IDentifier (ID) and a password of an application for using of the service from the authentication server, transmitting, to the service providing server, a service request message comprising the first access information, performing a connection procedure with a second device among the plurality of devices, obtaining from the connected second device, second device information, and after registering the second device to the service providing server based on the second device information, transmitting, to the second device, registration information comprising the authentication code. The authentication code is used to request second access information of the second device to the authentication server.