1. A parking camera system, the system including: a plurality of cameras equipped with a vehicle; an image synthesizer configured to synthesize at least one image photographed by at least one of the plurality of cameras; a controller configured to receive an input signal selecting a parking mode and receive steering angle information; a memory configured to store a parking guide line of the vehicle and a parking area image for each parking mode and output to the image synthesizer the parking guide line or the parking area image according to the selected parking mode; and an estimated travel trajectory generating and overlaying processor configured to generate an estimated travel trajectory of the vehicle by receiving the steering angle information of the vehicle from the controller, and synthesizing the estimated travel trajectory of the vehicle with the at least one image synthesized by the image synthesizer, wherein the image synthesizer synthesizes at least one or more of the parking guide line and the parking area image with the at least one images photographed by the at least one of the plurality of cameras, and wherein the image synthesizer simultaneously displays four images on a display, the images including a front view, a rear view, a left view and a right view.