To obtain an epoxy resin composition capable of eliminating or shortening a post-mold curing step after sealing a semiconductor element.

This epoxy resin composition comprises an epoxy resin containing an epoxy resin represented by the formula (each R is the same or different atom or group selected from hydrogen, halogens and alkyl groups) in an amount of 30-100 wt.% in the total amount of the epoxy resin, a phenol resin, an inorganic filler containing a fused crushed silica in an amount of 20-100 wt.% in the whole inorganic filler, a curing accelerator and MgXAlY (OH)2X+3Y-2Z(CO3)Z.mH2O [0<Y/X≤1; 0≤Z/Y<1.5; (m) is a positive number] in an amount of 0.1-5 wt.% in the whole resin composition.