A device includes an amplifier for amplifying and supplying a high frequency power supplied to a load, a parameter detector for detecting a parameter of a current, a voltage, or a power from the amplifier to the load, a current supply unit for supplying a driving current for the amplifier, and an output unit for outputting a command signal for changing an amplification degree of the amplifier based on the detected parameter such that the parameter becomes a target value. The device further includes a first abnormality detector for detecting an abnormality by monitoring the command signal, and/or a current detector for detecting the driving current, a current data storage unit storing an upper and a lower limit value of the driving current, and a second abnormality detector for detecting the abnormality based on at least one of the upper limit value or the lower limit value.