Data retransmission processing method and apparatus therefor

The present invention relates to a data retransmission processing method and an apparatus therefor and, more specifically, to a method and apparatus for a hybrid automatic repeat request (HARQ) operation of a terminal and a base station which perform communication using an unlicensed band cell. In particular, the present invention provides a method and apparatus for processing data retransmission by a terminal, the method comprising the steps of: performing downlink data reception or uplink data transmission in the unlicensed band cell; receiving downlink control information including scheduling information for HARQ retransmission when the downlink data reception or the uplink data transmission fails; and performing the HARQ retransmission for downlink data or uplink data in a licensed band cell, wherein the unlicensed cell is a cell using a frequency in an unlicensed band which one or more communication systems share.