Disclosed is a method and apparatus for transmitting data in a non-licensed band. The method of transmitting downlink data in the non-licensed band may comprise the steps of: generating, by a base station, downlink data and transmitting the downlink data to a terminal through a downlink subframe. The downlink data may comprise wireless LAN preamble, PDCCH data, and PDSCH data. The wireless LAN preamble may comprise information on time resources for communication between the base station and the terminal, and the PDCCH data may comprise control data for the terminal. Also, the PDSCH data may comprise traffic data for the terminal.