The present invention has as its object to inhibit fracture due to a HAZ softened part in substantially circular laser lap welding taking the place of resistance spot welding for joining a superposed plurality of steel sheets including a high strength steel sheet.To solve this problem, the inventors discovered lap welding comprising superposing a plurality of steel sheets and firing a laser to form a substantially circular laser weld (1), which lap welding firing the laser in a straight line through an outer edge of the substantially circular laser weld (1) so as to form a hardened part (8) at the steel sheets and thereby suppressing fracture arising from the HAZ softened part.