Provided is an insulated electric wire, a wire harness, and a composition for an electric wire coating material with which the amount of a filler, which is the flame retardant, can be reduced as much as possible without using electron beam crosslinking, the composition having a high heat resistance, a high gel fraction, flexibility, and good workability of assembling a wire harness. An electric wire coating material is made of a composition comprising (A) a silane-grafted polyolefin obtained by grafting a silane coupling agent onto a polyolefin having a density of 0.855 to 0.885 g/cm3, (B) an unmodified polyolefin having a density of 0.890 to 0.955 g/cm3, (C) a modified polyolefin modified by one or more functional groups selected from a carboxylic acid group, an acid anhydride group, an amino group, an acrylic group, a methacrylic group, and an epoxy group, (D) a bromine-based flame retardant and antimony trioxide, (E) a crosslinking catalyst batch, (F) zinc oxide and an imidazole-based compound, or zinc sulfide, (G) an antioxidant, (H) a metal deactivator, and (I) a lubricant.