An ignition coil of a dual ignition type that can prevent outputs from becoming unbalanced due to a difference in floating capacitance on wiring that connects secondary output terminals and ignition plugs together, thus realizing balanced outputs. A coil assembly housed in a housing as a coil case has a primary coil and secondary coils disposed concentrically with the primary coil. The secondary coils are comprised of two coils wound in opposite directions with the center of winding width being a boundary. The center of the winding width of the primary coil is shifted from the center of the winding width of the secondary coils by a predetermined width so as to balance outputs from the two secondary coils. A casting material is filled into a gap between the housing and the coil assembly and gaps which the coil assembly has.