Disclosed in the present invention are an apparatus and a method for manufacturing a rotor blade capable of being casted in to a minute form by making molten metal be completely permeated into a mold by fixating the mold in a vacuum chamber while injecting the molten metal using a gravitational method to perform a vacuum exhaust. The present invention, regarding an apparatus for manufacturing a rotor blade by melting an alloy having a low fluidity, includes a vacuum chamber having at least one exhaust hole while maintaining a vacuum state on the inside; an injection passage mounted inside the vacuum chamber to which molten metal is injected from the top; and multiple porous molds formed on one side of the injection passage.