produced with the ignition in the combustor 2 a is propagated to the adjacent combustor 2 b through the flame propagating pipe 10 a likewise a flame produced in the combustor 2 f is propagated to the adjacent combustor 2 e through the flame propagating pipe 10 e subsequently the flame is propagated from the combustor 2 b to the combustor 2 c through the flame propagating pipe 10 b while the flame is propagated from the combustor 2 e to the combustor 2 d through the flame propagating pipe 10 d in this way the flame is successively propagated from one combustor to the next adjacent combustor in two opposite directions so that all the combustors are eventually ignited further in the example shown in fig4 the flame sensors 22 are mounted to the combustors 2 d 2 e other than the combustors 2 a 2 f provided with the ignition plugs 29 when those two flame sensors 22 detect flames it is determined that all the combustors have been ignited with such a method of detecting a flame by the flame sensor 22 however the flame sensor 22 must be mounted to the combustor 2 also since the combustor is subjected to an atmosphere at high temperatures under high pressures the flame sensor 22 must be highly durable against such an atmosphere further a cooling device such as a water cooling jacket or an air cooling device for cooling the flame sensor 22 is required in some cases in view of the above described situation the gas turbine of the illustrated embodiment is intended to detect the establishment of ignition in the combustor by the following method with no need of using any flame sensor 22 fig5 shows one example of behavior of the gas turbine.