The present invention relates to a wireless communication system. More specifically, the present invention relates to a method and a device for canceling a scheduling request triggered by a sidelink buffer status report in a D2D communication system, the method comprising: triggering one or more sidelink Buffer Status Reports (BSRs) for sidelink data available for transmission; triggering one or more Scheduling Requests (SRs); configuring one or more sidelink grants in one or more subframes within a certain period; checking, in a first subframe, whether remaining sidelink grants can accommodate all pending data available for transmission; and canceling the all of the one or more triggered SRs if the all of the one or more triggered SRs are triggered by the one or more sidelink BSRs and the remaining sidelink grants can accommodate all of the pending data available for transmission, wherein the remaining sidelink grants are sidelink grants configured in one or more subframes starting from the first subframe to end of the certain period.