A foreign substance removal apparatus for a gas turbine, comprising: a combustor casing having a cylindrical shape, configured to be non-rotating and fixed at a rear end of a compressor of the gas turbine and having a first cooling air passage formed in a tangential direction of the combustor casing for moving cooling air into an inner hollow region formed therein and obliquely extending towards a torque tube; a first foreign substance collection unit for primarily filtering foreign substances contained in the cooling air and disposed at a position adjacent to a lower end of the first cooling air passage, wherein the first foreign substance collection unit is one of a groove and a slit extending inward of the torque tube facing the first cooling air passage by a predetermined length and/or wherein the first foreign substance collection unit is disposed in a circumferential direction of the combustor casing, and comprises a first chamber facing an inner upper portion of the combustor casing and a first filter part provided in the first chamber; a second cooling air passage extending radially in a circumferential direction of the torque tube located in the combustor and toward a turbine blade; and a second foreign substance collection unit disposed on a flow path in the second cooling air passage and communicating with the second cooling air passage for secondarily filtering foreign substances contained in the cooling air introduced through the first cooling air passage, wherein the second foreign substance collection unit is disposed in the circumferential direction of the torque tube, and comprises: a diameter reduction part having a reduced diameter as directed outward from a center thereof in a radial direction of the torque tube; and a second chamber formed above the diameter reduction part and having a space for storage of collected foreign substances. a combustor casing having a cylindrical shape, configured to be non-rotating and fixed at a rear end of a compressor of the gas turbine and having a first cooling air passage formed in a tangential direction of the combustor casing for moving cooling air into an inner hollow region formed therein and obliquely extending towards a torque tube; a first foreign substance collection unit for primarily filtering foreign substances contained in the cooling air and disposed at a position adjacent to a lower end of the first cooling air passage, wherein the first foreign substance collection unit is one of a groove and a slit extending inward of the torque tube facing the first cooling air passage by a predetermined length and/or wherein the first foreign substance collection unit is disposed in a circumferential direction of the combustor casing, and comprises a first chamber facing an inner upper portion of the combustor casing and a first filter part provided in the first chamber; a second cooling air passage extending radially in a circumferential direction of the torque tube located in the combustor and toward a turbine blade; and a second foreign substance collection unit disposed on a flow path in the second cooling air passage and communicating with the second cooling air passage for secondarily filtering foreign substances contained in the cooling air introduced through the first cooling air passage, wherein the second foreign substance collection unit is disposed in the circumferential direction of the torque tube, and comprises: a diameter reduction part having a reduced diameter as directed outward from a center thereof in a radial direction of the torque tube; and a second chamber formed above the diameter reduction part and having a space for storage of collected foreign substances. a diameter reduction part having a reduced diameter as directed outward from a center thereof in a radial direction of the torque tube; and a second chamber formed above the diameter reduction part and having a space for storage of collected foreign substances.