To provide an inexpensive compact gas turbine device which can drive a vertical or slanting drive shaft of a pump by a horizontal gas generation turbine.

This gas turbine device has a turbine compressor 13 for compressing air, a first turbine 14 whose rotary shaft is coaxially joined to the rotary shaft 15 of the compressor 13 and is rotated by air compressed by the compressor 13, an output turbine 8 which is rotated by the combustion gas passing through the first turbine 14 and has an output shaft 17 disposed at right angles to the rotary shaft 15 of the first turbine 14, a bent duct 6 for joining the inlet and the outlet of the combustion gas of both turbines 14, 8, and a speed reduction device 9 joined to the end of the output shaft 17 of the output turbine 8. The extension of the output shaft 10 of the speed reduction device 9 is between the turbine compressor 13 and the output shaft 17 of the output turbine 8.