An epoxy resin composition for encapsulating a semiconductor element and a semiconductor device manufactured using the epoxy resin composition are provided. The epoxy resin composition includes epoxy resin, a curing agent, at least one kind of an inorganic filler selected from the group consisting of silicates such as talc and calcined clay, oxides such as silica and fused silica, and hydroxides such as aluminum hydroxide and magnesium hydroxide, and a pH buffer agent having a pH buffer area of pH 4 to 8. Further, the semiconductor device is manufactured by encapsulating at least one semiconductor element with a cured product of the above epoxy resin composition. Such a semiconductor device can have excellent moisture resistance.