To certainly detect generation or extinguishment of a flame by providing a flame detector on a gas turbine combustion chamber and detecting ultraviolet ray of a flame state of a combustion gas.

An air compressor 3 compresses an atmosphere suctioned by a variable guide vane 2 to a high pressure and the high pressure air is supplied to a turbine combustion chamber 5 with a fuel. A combustion gas produced here is expanded in a gas turbine 1 and the air compressor 3 and a generator 4 are rotated and driven by a rotation torque generated at the time of expansion. Whereas, one or more flame detector 6 assembled in the gas turbine combustion chamber 5 particularly detects a light signal of an ultraviolet ray by a sensor accommodated in a cylindrical body during a flame state of the combustion gas and converts it into an electric signal to output it. A comparator 10 of a fire monitoring operator 7 warns an operator by an alarm 11 when an actual electric signal inputted from the flame detector 6 is below a set signal for the decision of existence or non-existence of a generation or an extinguishment of flame from a setting device 9 carrying out a comparison. Thereby, existence or non-existence of a local high temperature of the combustion gas can be certainly detected.