The present invention relates to a combustion efficiency improver capable of effectively improving combustion efficiency of various fossil fuels to significantly increase the steam production, reducing the concentration of combustion flue gas, enhancing deacidification ability, and inhibiting the growth of clinkers in a combustion furnace, and to the use thereof. The combustion efficiency improver for increasing the steam production of the present invention comprises: a dissolving agent composed of sodium hydroxide and potassium hydroxide; an oxygen supplying agent composed of hydrogen peroxide; and a clinker inhibitor, and characteristically, the combustion efficiency improver comprises: a dissolving agent composed of sodium hydroxide and potassium hydroxide; a clinker inhibitor composed of at least one of borax and sodium borate; hydrogen peroxide; propylene glycol; and water. The combustion efficiency improver for increasing the steam production of the present invention, which is configured as above, is provided by adding a predetermined proportion of propylene glycol containing a bivalent alcohol group to the composition composed of the dissolving agent, the clinker inhibitor, and hydrogen peroxide, so that a conventional clinker inhibitor is easy to dissolve; the generation of nitrogen oxides can be suppressed due to the use of propylene glycol; the temperature in a fire box can be increased due to characteristics of the agent containing an alcohol group, leading to a great amount of steam produced even with a small amount of incineration; the growth of clinkers can be inhibited in the fire box; and the convenience of operation can be dramatically improved.