In order for an in-app service providing system comprised of an in-app service server and a content server to provide a customized service to a user, when the in-app service server receives user information from a user terminal of the user, it checks whether or not the received user information has been previously stored. When the user information has been stored, user log information corresponding to the user information is received from the content server, and the in-app service server selects content to be provided to the user based on the user information and the user log information. When the content server generates a template including content, the in-app service server provides the template to the user terminal, thus providing a user-customized service.