A method for controlling bandwidth in a Voice over Internet Protocol (VoIP) system provided with gateways that are capable of performing real time bidirectional communication between endpoint terminals over the Internet, where the endpoint terminals include voice and image and/or data communication, includes the steps of calculating total bandwidth usage of each gateway upon receiving a call setup request from an endpoint terminal in consideration of the number of calls currently being processed and the bandwidth usage according to coder/decoder (codec) usage for each call, and transferring the calculated total bandwidth usage to other gateways in the VoIP system.