PURPOSE: To form an amplifier with an arrester low in loss at a high frequency band by providing an electromagnetic coupling type filter to an input terminal or an output terminal of the amplifier.

CONSTITUTION: Electromagnetic coupling type filters 13, 14 are provided to an input and output path of a high frequency signal for an amplifier 4 in a high frequency amplifier provided with the amplifier 4 and a metal made case 9 connecting to ground and with an arrester 10 at a feeder 12 of the amplifier 4 at the outside of the case 9 so that no effect is given onto the high frequency circuit a voltage and a current caused by lightning are blocked. Since no arrester 10 is included in a transmission system (path) of the high frequency signal in this way, even if lightning takes place and a large voltage and a large current are applied to the transmission system, no fluctuation is caused to the level of the high frequency signal and it is not required to take the increase in the insertion loss of the high frequency signal transmission system due to the insertion of the arrester into account even at the increase in the operating frequency band and the design of the amplifier is facilitated.