To provide an ignition coil for an internal combustion engine, which has a groove sectioned with a plurality of collars at an outer periphery of a secondary bobbin to be wound with a secondary coil and also has an electric wire for the secondary coil divided and wound around the groove, the ignition coil for the internal combustion engine being compact and lightweight and having little dielectric breakdown between a crossover line and adjacent winding layers without making small the width of a slit for the crossover line provided in the collar.
A small partitioning rib is formed at a slit bottom part for crossing of the electric wire for the secondary coil between wiring layers. Namely, when a divided wiring pattern of the secondary coil 2 is formed, the slit 5b is formed in the collar 5a of the secondary bobbin 5, and the crossover line 2b passes through the slit 5b, so that a plurality of successive winding layers are formed of the one electric wire. A small partitioning rib 8 is formed on a low-voltage side of the bottom part of the slit 5b. In the coil, slack of the crossover line is suppressed, winding swell at the slit part and falling of the collars can be suppressed, and an insulation distance between the wiring layer and crossover line can be made stable to avoid dielectric breakdown between the crossover line and adjacent winding layers. If the crossover line 2b slackens toward the low voltage side, the small partitioning rib 8 serves as a stopper to prevent the crossover line 2b from being adjacent to the winding layers.