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.