Insulating resin composition and insulated electric wire

An insulating resin composition comprising:

• a resin component containing
• a first copolymer which is a copolymer of ethylene and an unsaturated hydrocarbon having 4 or more carbon atoms and which has a density of less than 0.88 g/cm3,
• a second copolymer which is a copolymer of ethylene and an unsaturated hydrocarbon having 4 or more carbon atoms, which is subjected to acid modification, and which has a density of less than 0.88 g/cm3, and
• a third copolymer which is a copolymer of ethylene and an acrylic acid ester or a methacrylic acid ester,
• wherein a content of the second copolymer is 10% by mass or more of a total content of the first copolymer, the second copolymer, and the third copolymer, and
• a ratio (mass ratio) of a total content of the first copolymer and the second copolymer to a content of the third copolymer is 100:0 to 40:60;
• and
• 30 to 100 parts by mass of a flame retardant and 1 to 5 parts by mass of a crosslinking assistant relative to 100 parts by mass of the resin component.