A combustor 20A of an embodiment includes: a combustor casing 70; a combustor liner 61 which is provided in the combustor casing 70 and combusts a fuel and an oxidant to produce a combustion gas; a pipe-shaped member 101 provided to penetrate the combustor casing 70 and the combustor liner 61; a heat-resistant glass 102 which is provided on the combustor casing side in the pipe-shaped member and closes the pipe-shaped member 101; a laser light supply mechanism 103 which irradiates an interior of the combustor liner 61 through the heat-resistant glass 102 and an interior of the pipe-shaped member with a laser light 110; and a contact prevention mechanism 104A which prevents a combustion gas in the combustor liner from coming into contact with the heat-resistant glass 102.