1. A method of providing information of interest to a user via a multimedia device of a plurality of multimedia devices used by the user, the method comprising: receiving a bookmark index of a first information object about the information of interest to the user; searching for the first information object from a first database according to the received bookmark index, the first database being independent of the plurality of multimedia devices and comprising the information of interest to the user, which is received from the plurality of multimedia devices used by the user; reading at least one piece of additional information that is mapped to the first information object from the first database; selecting additional information according to a type of the multimedia device from the at least one piece of additional information; converting the selected additional information into additional information having a format according to the type of the multimedia device; collecting web data from an external multimedia service including a web service by using a uniform resource locator (URL) and storing the collected web data in a second database; transmitting, from the first database to the multimedia device, the additional information having the format according to the type of the multimedia device, wherein the transmitting of the additional information to the multimedia device comprises: analyzing the first information object stored in the first database; calculating a user's preference from the first information object, and transmitting, to the multimedia device, a third information object having the user's preference greater than a predetermined threshold value among at least one second information object which is extracted from the collected web data and stored in the second database, and additional information about the third information object, according to the calculated user's preference.