Disclosed are channel management methods in a multicarrier structure in a mobile communication system. Uplink (UL) and downlink (DL) channel management methods in a carrier aggregation environment are used as the channel management methods. In DL, a base station determines a component carrier (CC) of an unstable radio channel state, stops data retransmission by the CC, and notifies a terminal of retransmission stop. In UL, the base station determines a CC of an unstable radio channel state and instructs the terminal to stop data retransmission by the CC, and the terminal stops the data retransmission and initializes a retransmission buffer. Using the channel management methods in the mobile communication system employing the multicarrier structure, an increase in the number of unnecessary retransmissions is prevented, so that unnecessary retransmission and power consumption of the terminal can be reduced and the waste of radio resources and the degradation of base station performance due to unnecessary retransmission can be prevented.