The present disclosure relates to an apparatus and method for controlling a downlink (DL) Hybrid Automatic Repeat reQuest (HARQ) timing in a system supporting a TDD-FDD joint operation and an FDD-TDD joint operation environment. A base station transmits a PDSCH and a UE transmits an HARQ response in response to the PDSCH. In the TDD-FDD joint operation, the interval between the PDSCH transmission and the HARQ response may be determined based on an FDD mode configuration when the PDSCH is transmitted through a TDD-based primary serving cell.