In this study, the thermal deformation of thin stainless steel sheet in laser micro-welding were experimentally and numerically investigated. The welding deformation was experimentally evaluated using a single-mode CW fiber laser with a high-speed scanning system. The numerical simulation was developed to calculate the temperature, stress and deformation fields. It was clarified that the laser irradiation condition has a significant effect on the welding mode and stress field. In addition, the thermal deformation was influenced by the weld bead geometry and residual stress distributions, and the final deformation was formed by residual stress and plastic deformation. It was found that the tensile stress was generated around the molten zone and balanced by the compressive stress in the base material.