A combustor (10) according to the invention includes: a combustor basket (14) in which compressed air and fuel are mixed with each other and the mixture is combusted; a transition piece (17) in which a tip portion of the combustor basket (14) is inserted with a gap (C) therebetween; a spring clip (19) that seals the gap between the combustor basket (14) and the transition piece (17); a throttle section (21) that is provided in an opening portion (Ck) of the gap (C) that is opened to the transition piece (17) on the tip side of the combustor basket (14), and narrows an opening area of the opening portion (Ck), compared to the base end side; and cooling device (22) for cooling the throttle section (21).