To provide a combustion system using wax grease as fuel for a burner.

This combustion system is provided with a reservoir device 400 for reserving the wax grease, and a second reservoir device 500 for reserving a usual fuel liquid. The wax grease is molten by heating with steam generated by heat from the burner 220, to serve as a fuel liquid in the reservoir device 400. A change-over mechanism 520 conducts optionally switching between the fuel liquid from the reservoir device 400 and the fuel liquid from the second reservoir device 500, to feed either thereof to the burner 220. The fuel liquid from the second reservoir device 500 is fed to the burner 220, at the time of burner 220 ignition, and the fuel liquid from the reservoir device 400 is fed to the burner 220, after the fuel liquid of certain level is reserved in the reservoir device 400 by the steam.