The present invention relates to a method and an apparatus for transmitting/receiving data, and a method for a user equipment transmitting data, according to one embodiment of the present invention, comprises: a step of determining conditions for determining whether a condition for transmitting short data is satisfied, when data to be transmitted is generated; and a step of including the data to be transmitted in a radio resource control (RRC) connection setup completion message and transmitting same, when the condition for transmitting the short data is satisfied. According to one embodiment of the present invention, the problem of network overload can be prevented by reducing signaling overhead when processing small packets, which are generated intermittently, in the mobile communication system, and an apparatus and a method for enhancing battery performance in the user equipment can be effectively provided.