An object is to provide an epoxy resin composition which exhibits excellent tracking resistance and additionally has excellent heat resistance with a Tg of 200° C. or higher and flame retardancy. Provided is an epoxy resin composition which contains a phosphorus-containing epoxy resin and a curing agent and has a phosphorus content of within a range of 1.0 to 1.8%, wherein the phosphorus-containing epoxy resin has a ratio (L/H) of 0.6 to 4.0 of the content of trinuclear bodies (L) to the content of hepta or higher nuclear bodies (H) measured by GPC, and is a product obtained from a novolac epoxy resin having an average number of functional groups (Mn/E) of 3.8 to 4.8 and a phosphorus compound represented by the following general formula (1) and/or general formula (2).