PURPOSE: To treat solid combustible material without dividing and to facilitate a combustion control by submerging a part except an end of the material together with a combustion base in water, igniting the end, and telescopically moving a burning part into or from the water in response to a burning state of the ignited material.

CONSTITUTION: Water is filled in a water tank 2, a combustion base 6 is moved above a water surface, gunpowder such as propellant, etc., of a rocket is set to the base 6, its end remains on the water surface by considering a burning velocity responsive to a type of the propellant, and the other is submerged together with the base 6 in the water. When the propellant is ignited, the propellant starts to be burnt at once, and hence the base 6 is vertically moved in response to a burning state, and the base 6 is raised to match an optimum burning velocity. When an abrupt combustion occurs, the base 6 is moved down to submerge the propellant in water and to be extinguished. Thus, an abnormal combustion can be rapidly and safely coped with.