Abstract: An insulating film having good thermal resistance and flame retardance, flexibility, and good wiring property and a flat cable that uses such an insulating film are provided. An insulating film includes a resin film, an anchor coat layer, and a flame-retardant resin layer stacked in that order. The flame-retardant resin layer is composed of a resin composition that contains 60 parts by mass or more and 240 parts by mass or less of a flame retardant-imparting agent relative to 100 parts by mass of a polypropylene resin having a flexural modulus of 100 MPa or more and less than 900 MPa on the basis of JIS K7171.