An internal combustion engine ignition coil according to the present invention includes: a central iron core; a primary coil disposed on an outer circumference of the central iron core; a secondary coil disposed on an outer circumference of the primary coil; a side iron core disposed on an outer circumference of the secondary coil; and an insulating material sealing the central iron core, the primary coil, and the secondary coil on an inner side of the side iron core. A first layered silicate having a particle diameter less than a winding diameter of the secondary coil is present at a higher concentration in a vicinity of the secondary coil than that in a vicinity of the side iron core in the insulating material. A second layered silicate having a particle diameter greater than the winding diameter of the secondary coil is present at a higher concentration than that of the first layered silicate between the outer circumference side of the secondary coil and the side iron core. The second layered silicate has an aspect ratio of 50 or more, the aspect ratio being a ratio of a long side of a particle of the layered silicate to a thickness of the particle.