A peaking circuit for adjusting peaking of a high-frequency signal, comprises: a first inductor; a second inductor which is electromagnetically coupled with the first inductor; a signal input section which receives an input signal; a transistor which adjusts electric current passing through the second inductor according to the input signal inputted via the signal input section; and a signal output section which outputs a signal whose peaking has been adjusted by the first inductor. Mutual inductance of the electromagnetically coupled first and second inductors is changed by the adjustment of the electric current passing through the second inductor, according to the input signal inputted via the signal input section, with the use of the transistor, thereby adjusting the peaking of signal waveform of electric current passing through the first inductor, and the signal subjected to the peaking adjustment is outputted from the signal output section.