Microarea strain distribution in real ridge waveguide laser diodes composed of InGaN/AlGaN/GaN lattice-mismatched heterostructure have been studied by high-resolution microbeam X-ray diffraction using highly collimated sub-μm beam. By the microarea mapping of X-ray diffraction, we confirmed the distribution change of lattice strain around ridge stripe region due to the change of biaxial tensile strain of p-type AlGaN layer. We found that the strain distribution in the ridge waveguide laser diode is not uniform around the ridge stripe region.