A fluororesin having a reactive functional group, wherein the difference between the loss elastic modulus at 270 C. of the fluororesin (G.sub.270) and the loss elastic modulus at 280 C. of the fluororesin (G.sub.280) (G.sub.270-G.sub.280) is 2,500 Pa or more. Also disclosed is a fluororesin layer containing the fluororesin; and a non-fluororesin layer containing a non-fluororesin.