Disclosed is a fuel tank which is excellent in moldability, chemical resistance and low fuel permeability, while exhibiting excellent recyclability. Specifically disclosed is a fuel tank composed of a main body and a bag-like fuel reservoir unit contained within the main body and having an internal volume changing according to the fuel amount. This fuel tank is characterized in that the fuel reservoir unit has a single-layer structure composed of a fluororesin, a multilayer structure composed of fluororesin layers, or a multilayer structure composed of a fluororesin layer and a thermoplastic resin layer.
