To provide an epoxy resin composition enabling it to fill an inorganic filler therein by an amount higher than a conventional level and having an excellent fluidity, and to provide a semiconductor device obtained by sealing a semiconductor element using this epoxy resin composition.

In an epoxy resin composition comprising, essentially, (A) an epoxy resin, (B) a phenol resin, (C) a curing accelerator and (D) an inorganic filler, this epoxy resin composition is specified by that the relative standard deviation of the ratio of the peak area derived from the epoxy resin to that derived from the phenol resin, which is obtained by pyrolysis GC/MS(gas chromatography/mass spectrometry), is ≤10 and the semiconductor device is obtained by sealing a semiconductor element using this composition.