Variable heat/power ratio cogeneration system

A variable heat/power ratio cogeneration system is provided, which is capable of suppressing the amount of NOx emission to the minimum level while ensuring the stability of combustion of a gas turbine combustor even when the ratio of gasification gas to be used to a normal fuel (such as natural gas or light fuel oil) to be used is changed or the composition of the gasification gas fuel are changed. The variable heat/power ratio cogeneration system includes: a first steam system (301) that injects extra steam on the upstream side of a flame zone with respect to the flow of combustion gas in the combustor (2); a second steam system (302) that is branched from the first steam system (301) and injects extra steam on the downstream side of the flame zone with respect to the flow of the combustion gas in the combustor(2); a first steam flow rate control valve (311) capable of controlling the flow rate of the steam to be injected by the first steam system (301); a second steam flow rate control valve (312) capable of controlling the flow rate of the steam to be injected by the second steam system (302); and a controller (400) that controls the first steam flow rate control valve (311) on the basis of the flow rate of the gasification gas and the flow rate of the normal fuel and controls the second flow rate control valve (312) on the basis of a demanded steam amount necessary for a steam consumption facility.