An induction heating apparatus which continuously heats a steel plate using a solenoid system, the apparatus comprising: at least three heating coils (10A-10D) disposed along a longitudinal direction of the steel plate to make the steel plate pass through an inside thereof; and characterized in that inductance adjusters are disposed on electrical pathways electrically connecting each of said heating coils (10A-10D) and a power source applying a voltage to each of said heating coils (10A-10D), the inductance adjusters (12A-12D) being capable of generating self-induction and adjusting self-inductance in the self-induction, and said inductance adjuster (12A-12D) being provided to each of said heating coils (10A-10D), wherein a mutual distance of said heating coils (10A-10D) mutually adjacent to one another is not less than 1/10 nor more than 1/3 of an inside diameter in a height direction of said heating coil (10A-10D); each of said inductance adjusters (12A-12D) is structured by forming bypassed paths in a direction orthogonal to the electrical pathway; and a space between said mutually adjacent inductance adjusters (12A-12D) is 50 mm to 500 mm so that each of said inductance adjusters (12A-12D) causes a generation of mutual induction at least between said inductance adjusters (12A-12D) mutually adjacent to one another; and wherein each of said inductance adjusters (12A-12D) generates the self-induction by bypassing the electrical pathway on which each of said inductance adjusters (12A-12D) is disposed in a substantially coil shape, and adjusts the self-inductance in the self-induction by changing a cross-sectional area of an area surrounded by the substantially coil-shaped bypassed paths being the bypassed electrical pathway. at least three heating coils (10A-10D) disposed along a longitudinal direction of the steel plate to make the steel plate pass through an inside thereof; and characterized in that inductance adjusters are disposed on electrical pathways electrically connecting each of said heating coils (10A-10D) and a power source applying a voltage to each of said heating coils (10A-10D), the inductance adjusters (12A-12D) being capable of generating self-induction and adjusting self-inductance in the self-induction, and said inductance adjuster (12A-12D) being provided to each of said heating coils (10A-10D), wherein a mutual distance of said heating coils (10A-10D) mutually adjacent to one another is not less than 1/10 nor more than 1/3 of an inside diameter in a height direction of said heating coil (10A-10D); each of said inductance adjusters (12A-12D) is structured by forming bypassed paths in a direction orthogonal to the electrical pathway; and a space between said mutually adjacent inductance adjusters (12A-12D) is 50 mm to 500 mm so that each of said inductance adjusters (12A-12D) causes a generation of mutual induction at least between said inductance adjusters (12A-12D) mutually adjacent to one another; and wherein each of said inductance adjusters (12A-12D) generates the self-induction by bypassing the electrical pathway on which each of said inductance adjusters (12A-12D) is disposed in a substantially coil shape, and adjusts the self-inductance in the self-induction by changing a cross-sectional area of an area surrounded by the substantially coil-shaped bypassed paths being the bypassed electrical pathway.