A method for producing an epoxy resin composition for semiconductor encapsulation, which does not cause void generation and the like and is excellent in reliability. A method for producing an epoxy resin composition for semiconductor encapsulation, which contains the following components (A) to (C): (A) an epoxy resin, (B) a phenol resin, and (C) a hardening accelerator, which comprises mixing the whole or a part of the components excluding the component (A) among the components containing the components (A) to (C) in advance under a reduced pressure of from 1.333 to 66.65 kPa and under a heating condition of from 100 to 230.degree. C., and then mixing the component (A) and remaining components with the resulting mixture.