Disclosed in the present invention is a method for a first user equipment inside a coverage area of a base station conducting device-to-device communication with a second user equipment outside the coverage area in a wireless communication system. More specifically, the method comprises the steps of: dividing into a plurality of candidate sections a specific time unit for the device-to-device communication; and transmitting a reference signal for obtaining synchronization to the second user equipment from one section from among the candidate sections, when a random number that is generated is bigger than or equal to a critical value corresponding to the inside of the coverage area, wherein the critical value corresponding to the inside of the coverage area is smaller than a critical value corresponding to the outside of the coverage area.