The present invention relates to a wireless communication system. More specifically, the present invention relates to a method and a device for allocating uplink resources in the wireless communication system, the method comprising: transmitting, by a first eNB to a second eNB, uplink (UL) resource allocation information for a user equipment (UE) connected with both the first eNB and the second eNB; receiving, by a first eNB from the UE, buffer size information; allocating one or more UL resources to the UE, by considering both of the buffer size information and the UL resource allocation information, wherein the UL resource allocation information indicates a ratio of the buffer size to be considered in each eNB.