Welded portion inspection apparatus and inspection method thereof, with inspection in different zones of the molten pool

A welded portion inspection apparatus that inspects a welding state of a welded portion formed at the time when a plurality of workpieces is welded, the welded portion inspection apparatus comprising:

• a laser beam radiation portion that radiates a welding laser beam several times along one welding locus set in the workpieces so as to weld the workpieces, or radiates an inspection laser beam several times along one scanning locus set in a molten pool of the workpieces that are molten by the welding laser beam;
• a laser-receiving sensor that receives a returned light beam including at least one of reflection light of the welding laser beam or the inspection laser beam radiated by the laser beam radiation portion, the reflection light being reflected from the molten pool of the workpieces, vapor light caused due to melting and evaporation of the workpieces, and thermal radiation light emitted from the molten pool of the workpieces;
• and
• a measuring instrument that monitors an intensity of a returned light beam received by the laser-receiving sensor in a first region inside the molten pool of the workpieces which is relatively close to a given point and an intensity of a returned light beam received by the laser-receiving sensor in a second region inside the molten pool of the workpieces which is relatively spaced from the given point, in order to inspect a welding state of a welded portion of the workpieces.