In an inspection for protrusion of the melted thermoplastic material of transversal line seal into inside, it is an object to provide a quality inspection method and a quality inspection device which can easily detect projection on edge of seal, securely capture even fine unevenness which could not visually found, and allows for accurate and reliable inspection without variation of inspection.The quality inspection method comprise steps of returning container formed from a web-like packaging laminated material to a shape of pillow-like preliminary forming, cutting container wall to sample a filled food, preparing the sampled body, measuring an edge of the transversal seal zone on the inside of the container over the whole length of the outer surface of the edge for unevenness of the outer surface by a detecting unit, and judging an acceptability of the transversal seal zone based on signals from the detecting unit by an analyzing unit.