A traffic information service apparatus using an ad-hoc network and a method for controlling the same. The apparatus provides an ad-hoc network between vehicles and roadside devices, and collects/provides traffic information using the ad-hoc network. The method for providing a user with traffic information, comprising the steps of a) allowing vehicles to broadcast their registration messages to create an ad-hoc network, and creating the ad-hoc network between the vehicles on the basis of the registration messages, b) allowing a Road Side Equipment (RSE) to receive the registration messages broadcast from the vehicles, and collecting traffic information from the registration messages, and c) allowing the RSE to transmit the traffic information to a traffic information service center.