A new method of the X-ray stress measurement was proposed for measuring the residual stress in Al thin films having the [111] fiber texture with the fiber axis perpendicular to the film surface. The strain was measured from Al 222 and 311 diffractions obtained by Cr-Kα radiation. The values of in-plane residual stresses σ11, σ22 and σ12, and out-of-plane normal residual stress, σ33 were determined from the measured strains by using the fundamental formulae derived on the basis of Reuss and Voigt models. The measured residual stress in the thin films was nearly equi-biaxial tension. The magnitude of the tensile residual stress decreased with increasing film thickness.