A pipe joint which includes: a cylindrical joint body (16, 16b, 16e, 16f, 16g, 95, 276) into which a pipe is inserted and which is configured to be capable of communicating with a refrigerant flow path (17, 17g) of a heat exchanging unit; a cylindrical clamping member (32, 80, 84) mounted to the joint body (16, 16b, 16e, 16f, 16g, 95, 276) by screwing; and a ferrule receiving an axial pressing force from the clamping member (32, 80, 84) screwed in a clamping direction, thereby airtightly sealing a gap between an inner periphery of the joint body (16, 16b, 16e, 16f, 16g, 95, 276) and an outer periphery of the pipe, a cylindrical fixing member (35, 66a, 66b, 66c, 66d, 66e, 66f, 81, 85, 93, 98, 271) constructing the clamping member (32, 80, 84) and abutting against the ferrule to impart a pressing force to the ferrule; a clamping nut (36, 70, 74, 82, 86, 88, 94, 272) constructing the clamping member (32, 80, 84) and having an outer periphery formed with a non-circular fitting portion, the clamping nut (36, 70, 74, 82, 86, 88, 94, 272) receiving a screw-in force in the clamping direction, thereby imparting to the fixing member (35, 66a, 66b, 66c, 66d, 66e 66f, 81, 85, 93, 98, 271) a pressing force to the ferrule side; and a locking unit preventing the fixing member (35, 66a, 66b, 66c, 66d, 66e, 66f, 81, 85, 93, 98, 271) from displacement in a direction such that the ferrule is released from the pressing force applied by the fixing member (35, 66a, 66b, 66c, 66d, 66e, 66f, 81, 85, 93, 98, 271), characterized in that the locking unit includes a cover (110a, 110b, 110c, 110d, 110e, 110f) which is configured to surround the fixing member (35, 66a, 66b, 66c, 66d, 66e, 66f, 81, 85, 93, 98, 271) and is rotatable relative to the fixing member (35, 66a, 66b, 66c, 66d, 66e, 66f, 81, 85, 93, 98, 271). a cylindrical joint body (16, 16b, 16e, 16f, 16g, 95, 276) into which a pipe is inserted and which is configured to be capable of communicating with a refrigerant flow path (17, 17g) of a heat exchanging unit; a cylindrical clamping member (32, 80, 84) mounted to the joint body (16, 16b, 16e, 16f, 16g, 95, 276) by screwing; and a ferrule receiving an axial pressing force from the clamping member (32, 80, 84) screwed in a clamping direction, thereby airtightly sealing a gap between an inner periphery of the joint body (16, 16b, 16e, 16f, 16g, 95, 276) and an outer periphery of the pipe, a cylindrical fixing member (35, 66a, 66b, 66c, 66d, 66e, 66f, 81, 85, 93, 98, 271) constructing the clamping member (32, 80, 84) and abutting against the ferrule to impart a pressing force to the ferrule; a clamping nut (36, 70, 74, 82, 86, 88, 94, 272) constructing the clamping member (32, 80, 84) and having an outer periphery formed with a non-circular fitting portion, the clamping nut (36, 70, 74, 82, 86, 88, 94, 272) receiving a screw-in force in the clamping direction, thereby imparting to the fixing member (35, 66a, 66b, 66c, 66d, 66e 66f, 81, 85, 93, 98, 271) a pressing force to the ferrule side; and a locking unit preventing the fixing member (35, 66a, 66b, 66c, 66d, 66e, 66f, 81, 85, 93, 98, 271) from displacement in a direction such that the ferrule is released from the pressing force applied by the fixing member (35, 66a, 66b, 66c, 66d, 66e, 66f, 81, 85, 93, 98, 271), characterized in that the locking unit includes a cover (110a, 110b, 110c, 110d, 110e, 110f) which is configured to surround the fixing member (35, 66a, 66b, 66c, 66d, 66e, 66f, 81, 85, 93, 98, 271) and is rotatable relative to the fixing member (35, 66a, 66b, 66c, 66d, 66e, 66f, 81, 85, 93, 98, 271).