PURPOSE: A micro crack welding method for a sheet material is provided to prevent changes due to chemicals by inducing convex bead without addition of a separate welding material. CONSTITUTION: A micro crack welding method for a sheet material is as follows. A material is installed on a jig(101) with a micro crack(C) facing up. A robot is driven to move a laser optic head(103) along the micro crack site on the material and irradiate laser beam(LB) of a conductive welding range onto the micro crack site so that the micro crack site is rapidly heated. Convex bead is occurred so that the micro crack site on the material is inflated by the convection of heating source. The welded part is cooled for a predetermined time.
