Ignition apparatus including spark plug that generates plasma

An ignition apparatus that ignites a mixture of air and fuel gas by plasma to generate an initial flame, the apparatus comprising:

• a spark plug that includes an inner conductor, a cylindrical outer conductor that holds the inner conductor thereinside, and a dielectric that is provided between the inner conductor and the outer conductor, and that generates plasma in a plasma formation space between the inner conductor and the outer conductor;
• an electromagnetic wave power supply that generates an electromagnetic wave to apply electromagnetic wave power to the spark plug;
• an evaluation section that evaluates a state of formation of the plasma;
• a determination section that determines a matching object of the electromagnetic wave based on an evaluation result by the evaluation section;
• and
• a coupled state control section that controls a matching condition of the electromagnetic wave so that the electromagnetic wave matches the matching object, wherein
• when the evaluation section evaluates that the state of formation of the plasma to be a first state in which the plasma is not generated in the plasma formation space, the determination section determines that the matching object is the mixture present in the plasma formation space, and
• when the evaluation section evaluates that the state of formation of the plasma to be a second state in which the plasma is generated in the plasma formation space, the determination section determines that the matching object is the plasma present in the plasma formation space.