A combustor of a gas turbine includes a nozzle plate to accommodate an arrangement of fuel injection nozzles; an outer cap coupled with the nozzle plate while surrounding an outer circumferential periphery of the nozzle plate; a plurality of first protrusions radially protruding from the outer cap toward a center of the outer cap, the first protrusions arranged in a circumferential direction of the outer cap; and a plurality of first guide holes arranged at the outer circumferential periphery of the nozzle plate in a circumferential direction, to be respectively engaged with the first protrusions. Each first guide hole communicates with a linear recess and with a first fixing recess disposed at an end of the linear recess. The combustor, and a gas turbine including the combustor, evenly distribute stress to the nozzle plate and the outer cap, while minimizing thermal deformation of combustor components in a high-temperature operating environment.