A high frequency generating device used in a plasma ignition apparatus according to embodiments includes an output unit and a control unit. The output unit outputs a high frequency to an antenna that irradiates the high frequency into a combustion chamber of an internal-combustion engine. The control unit instructs the output unit to output the high frequency on the basis of an ignition signal that controls a spark discharge by an ignition plug and a control signal that controls output of the high frequency. Moreover, the control unit determines, when one of the ignition signal and the control signal is input, whether or not the other signal is input within a predetermined detection period, and detects abnormality in an input path of the ignition signal or in an input path of the control signal when the other signal is not input within the predetermined detection period.