Disclosed are a method for controlling power and an apparatus therefor in a wireless communication system supporting device-to-device (D2D) communication. Specifically, a method for a terminal for controlling the transmission power of a physical sidelink discovery channel (PSDCH) in a wireless communication system supporting D2D communication comprises the steps of: calculating the sum of reception strengths of the total number of PSDCHs received from a set PSDCH reception period; and transmitting the PSDCH, wherein if the sum of reception strengths of the total number of PSDCHs is greater than a previously set threshold value, then the PSDCH to be transmitted is transmitted under the transmission power controlled by the terminal, and if the sum of reception strengths of the total number of PSDCHs is less than a previously set threshold value, then the PSDCH to be transmitted can be transmitted under the maximum transmission power.