A method for transmitting a physical sidelink shared channel (PSSCH), by a device-to-device (D2D) terminal, in a wireless communication system involves receiving a physical sidelink control channel (PSCCH) and a PSSCH transmitted in a resource region indicated by the PSCCH. If an energy measurement value with respect to the PSSCH is greater than a preset threshold, the method further involves selecting a transmission resource excluding the resource region in which the PSSCH has been transmitted; and transmitting a D2D signal by means of the selected transmission resource, wherein the threshold has a value that varies in accordance with whether or not the PSSCH is retransmission or the redundancy version (RV) of the PSSCH.