The present invention relates to a method by which a first device-to-device (D2D) terminal transmits a D2D signal in a wireless communication system, and a device therefor. More particularly, the method comprises the steps of: setting a D2D transmission power reference on the basis of a timing reference applied according to a D2D signal type; and transmitting a D2D signal to a second D2D terminal on the basis of D2D transmission power determined according to the D2D transmission power reference, wherein the D2D transmission power reference is configured using a power reference of a wide area network (WAN)-based physical uplink control channel (PUCCH) when the timing reference follows a downlink timing, and configured using a power reference of a WAN-based physical uplink shared channel (PUSCH) when the timing reference follows an uplink timing.
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