The objective of the present invention is to provide: a fuel tank that can prevent an increase in weight and can have reduced cost and working time during a production process, a main wing; an aircraft fuselage; an aircraft, and a mobile body. The fuel tank is provided with a structural member that uses a carbon-fiber-reinforced plastic of which the reinforcing material (15) contains carbon fibers and the matrix (17) contains plastic. The matrix (17) is imparted electrical conductivity. Also, a cut surface (11a) That is of the structural member and that is formed by the strcutural member being cut may be exposed within the fuel tank where a fuel is housed.