The present invention relates to a wireless communication system. More specifically, the present invention relates to a method and a device for performing an adaptive bundling transmission in wireless communication system, the method comprising: generating a uplink (UL) data to be transmitted for an uplink grant of a Hybrid-ARQ (HARQ) process; performing a new HARQ transmission of the UL data with resetting a counter of the HARQ process, performing a HARQ retransmission of the UL data, if the new HARQ transmission of the UL data fails, wherein the counter is counted each time a HARQ transmission of the UL data fails, wherein if the counter is equal to or larger than a threshold, the HARQ retransmission of the UL data is performed with bundling transmission.