The present invention provides a method of transmitting a channel quality indicator (CQI) in a wireless communication system. The method performed by a user equipment supporting a relatively shorter transmission time interval (S-TTI) than a legacy transmission time interval (L-TTI) includes determining predefined control channel-related overhead depending on whether S-TTI-based communication is performed and transmitting the CQI based on the determined predefined control channel-related overhead. If the S-TTI-based communication is performed, the predefined control channel-related overhead is identically determined between an S-TTI including a legacy physical downlink control channel (PDCCH) region and a S-TTI not including a legacy PDCCH region.