Provided is a method for retransmission in a mobile communication system; and, more particularly, to an integrated operation method of Automatic Retransmission Request (ARQ) and Hybrid Automatic Retransmission Request (HARQ) in a mobile communication system. The method includes the steps of: a) shifting to a 2nd layer waiting status upon receipt of 1st layer reception failure information in a sending status that a fragment block of 2nd layer transmission data is transmitted to the a receiver according to the predetermined retransmission number; b) shifting to a 1st layer receiving status upon receipt of 1st layer reception success information in the sending status; and c) shifting to the transmission completion status upon receipt of the 2nd layer reception success information in the sending status.