A method and apparatus for a user equipment (UE) operating based on a DRX (Discontinuous Reception) configuration are disclosed. According to these, the UE receives a message including configuration or reconfiguration of DRX; and monitors a PDCCH (Physical Downlink Control Channel) during an active time according to the configuration or reconfiguration of DRX. Here, the active time includes a time period during a PDCCH indicating a new transmission has not been received after receiving the message including configuration or reconfiguration of DRX.