Disclosed is a method for determining transmission power for transmitting uplink signals between terminals in a wireless communication system that supports terminal-to-terminal communication, and an apparatus therefor. A method in which a first terminal determines transmission power for transmitting an uplink signal to a second terminal in a wireless communication system that supports terminal-to-terminal communication comprises the following steps: estimating a channel state based on a second terminal-specific signal received from the second terminal; transmitting the estimated channel information to a base station; receiving a message, including information on a transmission power control factor, from the base station or from the second terminal; and determining transmission power for transmitting an uplink signal to the second terminal based on the received message.