Jamming attack may pose a significant threat to the wireless network by occupying the wireless channel used by legal nodes. As an important building block for anti-jamming strategies, jammer localization provides us the feasibility to eliminate the jammers from the networks and a few algorithms have been presented to this end. However, current algorithms mainly focus on locating the jammers equipped with omnidirectional antennas and are usually fail to cope with directional jammers. In order to bridge this gap, a Directional Jammer Localization Algorithm (DJLA) is put forward in this paper. At first, a collection protocol is designed to collect the information of boundary nodes and jammed nodes. Then, a range-free method is put forward to locate the jammer without relying on the propagation parameters. The proposed DJLA only depends on the localization of jammed nodes and boundary nodes and employs their geometry knowledge. The mean value of the intersections between the straight line that represents jammer's direction and the circumcircles is considered as the directional jammer's position. Finally, a series of experiments have been conducted to evaluate the localization performance of DJLA.