[Problem] To provide a combustion device of high combustion efficiency in which additional charging of combustion material containing solids is also possible, and an electric power-generating device using same. [Solution] The combustion method that burns combustion material inside a combustion device comprises: a process of charging the combustion material in the combustion chamber of the combustion device; a process of igniting and burning said combustion material; a process of supplying air or combustion-aiding gas (called “air, etc.” below) to the flame resulting from the combustion of said combustion material from outside of the flame; a process of secondary combustion of the combustion material by said air, etc.; and a process of smoke exhaustion; and in particular, comprises a process of additionally charging combustion material that at least contains solids into said combustion chamber during combustion of the combustion material.