Provided are a method and an apparatus for transmitting uplink data in a wireless communication system. Specifically, a first terminal transmits a random access preamble for requesting a connectionless transmission. The first terminal receives a random access response comprising scheduling information of the uplink data. The first terminal transmits the uplink data, a reference signal selected by the terminal and terminal identification information of the terminal from a first overlapping resource utilized by a second terminal. The first terminal receives, as a response for the uplink data, a response signal comprising a terminal identification information field containing terminal identification information corresponding to each reference signal.