An apparatus for controlling turbine blade tip clearance is provided. The apparatus for controlling turbine blade tip clearance includes a turbine casing configured to guide a flow of combustion gas, an actuator ring rotatably mounted outside the turbine casing, a plurality of turbine blades rotatably mounted inside the turbine casing, a plurality of ring segments surrounding tips of the turbine blades and installed to form a predetermined gap with each tip, a plurality of rotary shafts each configured to have one end connected to several of the plurality of ring segments and the other end extending radially from the turbine casing, a link member configured to rotate an associated one of the rotary shafts according to circumferential rotational motion of the actuator ring, and a pusher member provided at an inner end of the rotary shaft to move the ring segments radially inward by rotation of the rotary shaft, wherein the actuator ring rotates back and forth in a predetermined angular range by an actuator installed outside the turbine casing.