A combustion system includes a combustor having staging blocks and flashback detection units configured to detect flashbacks occurring in the staging blocks, and a combustion control device configured to stop a supply of a fuel for one of the staging blocks in which a flashback occurs based on a detection signal from one of the flashback detection units. The combustion control device includes a staging processing unit configured to instruct to supply the fuel or stop the supply of the fuel for each of the staging blocks based on a staging pattern in which an operating line is specified and a load adjustment unit configured to reduce an amount of load to a level at which the supply of the fuel for the one of the staging blocks is stopped when the detection signal is input from the one of the flashback detection units.