Catalytic combustion is an ultralow NOx combustion method, so it is expected that this method will be applied to a gas turbine combustor. However, it is difficult to develop a catalytic combustor because catalytic reliability at high temperature is still insufficient. To overcome this difficulty, we designed a catalytic combustor in which premixed combustion was combined. By this device, it is possible to obtain combustion gas at a combustion temperature of 1300°C while keeping the catalytic temperature below 1000°C. After performing preliminary tests using LPG, we designed two types of combustor for natural gas with a capacity equivalent to one combustor used in a 20 MW class multican-type gas turbine. Combustion tests were conducted at atmospheric pressure using natural gas. As a result, it was confirmed that a combustor in which catalytic combustor segments were arranged alternately with premixing nozzles could achieve low NOx and high combustion efficiency in the range from 1000°C to 1300°C of the combustor exit gas temperature.