An apparatus for controlling IEEE 802.15.4 physical layer operation state is provided. The physical layer operation state controlling apparatus defines an operation state of a physical layer including a Hardwired Low-MAC (HL-MAC) device in which functions of IEEE 802.15.4 MAC layer are hardwired, and includes a state module for controlling the operation state of the physical layer. The state module includes a Finite State Machine (FSM) for, when receiving an event for the operation state of the physical layer, transiting to a state module corresponding to the event and controlling the operation state of the physical layer; and an interrupt handler for converting an interrupt received from the physical layer to the event corresponding to a register of the state module and sending the event to the FSM. Hence, by means of the state machine for the IEEE 802.15.4 PHY, the IEEE 802.15.4 physical layer operation state can be controlled to optimize the operations of the upper MAC.