The present invention relates to a method for transmitting a user plane data in a small cell environment where a terminal is simultaneously connected to a macro cell and a small cell and an apparatus therefor, and more specifically a method for allowing a first base station to control the transmission of the user plane data of a terminal. The transmission includes based on at least one of load information and the measurement report information, determining the transmission of the user plane data by choosing a wireless bearer constructed through a second base station; transmitting a bearer establishment request message to a second base station; receiving a bearer establishment response message from the second base station; and transmitting an upper layer signaling containing at least one of cell identification information for the cell associated with the second base station, the cell index information of the second base station, and the data wireless bearer information constructed through the second base station to the terminal.