Monotonic and cyclic loadings were subjected to electrodeposited copper foils (thickness is 8 and 20 μm), and the deformation behavior was observed. In-situ X-ray stress measurement was carried out under monotonic loading. The tensile strength of 8 μm foil was higher than that of 20 μm foil. On the other hand, the elongation of 8 μm foil was smaller. When the plastic deformation occurred, difference between the X-ray stress and the applied stress became large. The difference of 20 μm foil was larger than that of 8 μm foil. Fatigue strength of 8 μm foil was also higher than that of 20 μm foil. The value of the full width at half maximum, FWHM, increased dramatically at the first cycle, and then the value became nearly constant. Just before fracture, the value increased again. The change in FWHM corresponded to the change in the accumulated ratchet strain.