Abstract: A flat-cable-coating material includes a base film, and a heat-bonding layer(P+V) laminated to the base film and containing at least a filler(P) and a thermoplastic resin(V). The mass ratio (P)/(P+V) changes in a direction along the thickness of the heat-bonding layer in an inclined distribution curve preferably so as to decrease from the inner surface of the heat-bonding layer on the side of the base film toward the outer surface of the heat-bonding layer from 90% by mass and to 50% by mass. The filler(P) includes at least a hydrated metal compound(P1) and the mass ratio (P1/P) of the mass of the hydrated metal compound(P1) to the mass of the filler(P) changes in a direction along the thickness of the heat-bonding layer in a distribution curve so that the mass ratio (P1/P) decreases from the inner surface of the heat-bonding layer on the side of the base film toward the outer surface of the heat-bonding layer from 80% by mass to 0% by mass.