The present invention relates to a method and a system for securing discovery information being transmitted through a direct radio signal in a wireless communication system which supports a device-to-device service, and a device-to-device communication method of a transmission terminal, according to one embodiment of the present invention, can comprise the steps of: synchronizing with a discovery resource cycle number; determining discovery channel logical timing information of a discovery physical channel through which discovery information is to be transmitted; generating security information by using a security key, the determined discovery channel logical timing information and the discovery information to be transmitted; and transmitting the discovery information including the security information through the discovery physical channel. According to one embodiment of the present invention, it is possible to prevent discovery information of a terminal to be wrongly transmitted due to a case where another rogue terminal receives and changes the discovery information of the terminal, or the like.