A wideband amplifier that exhibits an even amplification characteristic in a wide frequency range, prevents degradation from occurring due to a parasitic capacitance, and that exhibits a shortened group delay time. The wideband amplifier includes, as a load of a current output amplifying element, a parallel combination of bandpass filters comprising L-C parallel and L-C-R series resonance circuits. The bandpass filters each have a plurality of poles and have zeros therebetween in the s-plane and provide an improved even characteristic in a respective pass band. The output terminal of the amplifying element serves as the output terminal of the amplifier, resulting in no problem of group delay. The capacitive elements between the output terminal of the amplifier and the GND assimilate, as parts of their constants, the parasitic capacitance, thereby preventing degradation of the frequency characteristic.