Provided are a method and device that identify characteristics of data to be sent by a user equipment and send small-sized data via a control message. The data transmission method for the user equipment may include: generating IP data; determining whether the IP data corresponds to small data that has a size less than or equal to a preset reference size or matches identification information of a preset service; and transmitting the IP data through a connection management (CM) layer to the network by use of a control message.