Abstract: A fuel supply method for a gas turbine combustor having first and second stage combustion chambers. The method comprises supplying the fuel from only first stage fuel supply from the start of the gas turbine until its low output range so as to operate only the first stage combustion chamber, supplying the fuel from both first and second stage fuel supply in a high output range of the gas turbine including its maximum output so as to operate both first and second stage combustion chambers. The method makes it possible to reduce NO.sub.x without deteriorating the combustion performance by step-wise supplying a predetermined flow rate of the fuel when the second stage fuel is to be supplied and at the same time, step-wise reducing the same quantity of the fuel that is being supplied from the first stage fuel supply.