A gas turbine combustor, comprising: a casing; a combustion cylinder which is provided in the casing and combusts a fuel and an oxidant to produce a combustion gas; a pipe-shaped member having an open inner end portion and an open outer end portion to penetrate the casing and the combustion cylinder; a heat-resistant glass which is provided on the casing side in the pipe-shaped member and closes the pipe-shaped member; a laser light supply mechanism which irradiates an interior of the combustion cylinder through the heat-resistant glass and an interior of the pipe-shaped member with a laser light; a contact prevention mechanism, which uses a flow of a contact prevention fluid for preventing a combustion gas in the combustion cylinder from coming into contact with the heat-resistant glass via the open inner end portion of the pipe-shaped member; a cylinder body which demarcates a space between the casing and the combustion cylinder; wherein the pipe-shaped member penetrates the cylinder body; characterized in that the contact prevention mechanism comprises: a first fluid supply part which supplies a first fluid between the cylinder body and the combustion cylinder; and an ejection part, which is formed in the pipe-shaped member located between the cylinder body and the combustion cylinder, wherein the ejection part has a plurality of ejection holes formed in a circumferential direction of the pipe-shaped member and ejects the first fluid through the ejection holes into the pipe-shaped member. a casing; a combustion cylinder which is provided in the casing and combusts a fuel and an oxidant to produce a combustion gas; a pipe-shaped member having an open inner end portion and an open outer end portion to penetrate the casing and the combustion cylinder; a heat-resistant glass which is provided on the casing side in the pipe-shaped member and closes the pipe-shaped member; a laser light supply mechanism which irradiates an interior of the combustion cylinder through the heat-resistant glass and an interior of the pipe-shaped member with a laser light; a contact prevention mechanism, which uses a flow of a contact prevention fluid for preventing a combustion gas in the combustion cylinder from coming into contact with the heat-resistant glass via the open inner end portion of the pipe-shaped member; a cylinder body which demarcates a space between the casing and the combustion cylinder; wherein the pipe-shaped member penetrates the cylinder body; characterized in that the contact prevention mechanism comprises: a first fluid supply part which supplies a first fluid between the cylinder body and the combustion cylinder; and an ejection part, which is formed in the pipe-shaped member located between the cylinder body and the combustion cylinder, wherein the ejection part has a plurality of ejection holes formed in a circumferential direction of the pipe-shaped member and ejects the first fluid through the ejection holes into the pipe-shaped member. a first fluid supply part which supplies a first fluid between the cylinder body and the combustion cylinder; and an ejection part, which is formed in the pipe-shaped member located between the cylinder body and the combustion cylinder, wherein the ejection part has a plurality of ejection holes formed in a circumferential direction of the pipe-shaped member and ejects the first fluid through the ejection holes into the pipe-shaped member.