A combustion system is capable of using a petroleum pitch fuel, and is provided with a burner having a fuel supply pipe where a flame stabilizing plate is formed in a tip end of the same, and a high temperature maintaining unit for maintaining an atmosphere temperature at a vicinity of the flame stabilizing plate during operation higher than a softening point of the petroleum pitch fuel. Thus, even when the petroleum pitch is used as fuel, the burner does not become unusable due to adhesion/solidification of the petroleum pitch inside the burner and combustion operation can be continued for a long time.