Provided are a method and a device for transmitting an IWS (Inter-Working signal) of a femto base station in a wireless communication system. The femto base station generates a sequence of a preamble including information about a frequency band on which the femto base station operates, maps the IWS including the sequence of the preamble to a plurality of subcarriers on a frequency domain, and transmits the IWS to a terminal through the subcarriers. The IWS can be mapped to the plurality of subcarriers positioned on one equal OFDM (Orthogonal Frequency Division Multiplexing) symbol on a time domain or a plurality of preset RUs (Resource Unit).