A flame-retardant epoxy resin composition, as well as an electronic device, a laminated circuit board, a multilayered circuit board and a printed circuit board employing the flame-retardant epoxy resin composition are disclosed. The flame-retardant epoxy resin composition contains: an epoxy resin; an epoxy resin curing agent; and flame-retardant particles containing a metal hydrate. The flame-retardant particles are provided with a coating layer on the surfaces thereof and have a volume average particle diameter in a range from 1 to 500 nm.