To provide the caulking structure of a laminated iron core for improving a stability and the caulking strength of a lamination, minimizing the interlayer gap between laminated iron core pieces, and manufacturing the laminated iron core with high occupancy ratio, even if a thin plate material is used.

A caulking protrusion 11 is provided, and a plurality of the iron core pieces 10 are caulked and laminated via the caulking protrusion 11 in the caulking structure of the laminated iron core piece 10. The caulking protrusion 11 comprises a protrusion 12, formed on the back side of the iron core piece 10 and a recess 13 formed on the front side right over the protrusion 12. Inner and outer widths of the engagement cross section of the caulking protrusion 11 are made gradually narrow, starting from the front side to the back side of the iron core piece 10. If the maximum of the inner width of the engagement cross section is (a), the minimum of the inner width is b, the minimum of the outer width is c and the maximum of the outer width is d, a relationship d>a>c>b is satisfied.