Provided is a combustion apparatus that can positively prevent a combustible gas present in the vicinity from catching fire in performing prepurge, which involves exhausting air from a combustion chamber provided with a burner, before igniting the burner. The combustion apparatus 1 contains combustion control means 6 that ignites the burner after performing prepurge by use of a fan 4, and gas detection means 5 that is provided between an air supply port 7 and the fan 4 and detects the concentration of a combustible gas. The combustion control means 6 ascertains, before starting the prepurge, whether a combustible gas of a preset maximum concentration or higher is detected by use of the gas detection means 5 (STEP 1) and prohibits the prepurge by prohibiting the energization of the fan 4 when a combustible gas of the maximum concentration or higher has been detected (STEP 2).