The present invention relates to 5G or pre-5G communication system for supporting a higher data transmission rate after 4G communication system such as LTE. The present invention provides a method for transmitting data on the basis of a measurement of a channel of an unlicensed band in a mobile communication system, the method comprising the procedures of: selecting a random number for backoff counting; determining whether to decrement the random number by 1; decrementing the random number by 1 on the basis of the determining; determining whether the channel is idle by measuring the channel; completing the backoff counting if the random number becomes 0; and transmitting data by means of the channel if the backoff counting is completed.