Experimental study has been carried out to clarify the characteristics of liquid film thickness of an air water annular two-phase flow in a double tube bend (inner dia. of the outer tube is 25mm, outer dia. of the inner tube is 16mm and bend radius is 250mm). The distribution of liquid film thickness on the outer tube varies with both the air and liquid flow rate, whereas on the inner tube, it varies only with the air flow rate. The average liquid film thickness of the inner tube approaches an asymptotic value, which is determined by the air flow rate, with the increase of liquid flow rate. The average liquid film thickness of a cross section in the double tube bend coincides with that of a coiled single tube of the same hydraulic diameter. It was confirmed that the film inversion phenomenon on the outer tube occurs when the centrifugal force acting on the gas phase exceeds that of the liquid film.