An apparatus for distributing data traffic in heterogeneous wireless networks is provided. A terminal for transmitting data to a plurality of wireless networks, includes a transmission rule storing unit to store a data transmission rule with respect to the plurality of wireless networks, a data dividing unit to divide first data into a plurality of first data groups based on the stored data transmission rule, a transmission network selecting unit to select an individual transmission network for each divided data group from the plurality of wireless networks based on the determined data transmission rule, and a network access unit to transmit each data group to the selected transmission network.