A combustion control method for use in a catalytic combustion system having (a) a gaseous mixture inlet port, located at the upstream side of said catalytic combustion system, for the entrance of a fuel-air mixture; (b) an exhaust gas outlet port, located at the downstream side of said catalytic combustion system, for the exit of an exhaust gas; (c) a primary combustion chamber in which a catalyst body is disposed, said catalyst body being formed of a porous base material with numerous communicating holes that supports thereon an oxidation catalyst; (d) a secondary supply port, located downstream of said primary combustion chamber, for the supply of a gaseous mixture or air; and (e) a secondary combustion chamber located downstream of said secondary supply port; comprising such process that an excess air ratio of said primary combustion chamber is initially set above 1 and after the rate of combustion of said secondary combustion chamber exceeds a given level, combustion is made to take place, with the excess air ratio of said primary combustion chamber set below 1.