The present invention relates to a wireless communication system. More specifically, the present invention relates to a method and a device for notifying D2D communication, the method comprising: generating, by a first UE, a first identity (ID) according to a type of D2D (Device to Device) communication; generating, by a first UE, a first indicator indicating that the first UE is trying to perform the type of D2D communication with at least one second UE; and transmitting, by the first UE, a first MAC PDU (Medium Access Control Protocol Data Unit) including the first ID and the first indicator to that at least one second UE.