To provide an effect circuit that can give round-shaped distortion effect to a music signal.An effect circuit 1 includes a input resistor R2 that is connected to a negative input terminal of an operational amplifier U1, a feedback resistor VR1 that is provided between a positive input terminal of the operational amplifier U1 and an output terminal of the operational amplifier U1, zener diodes D1 and D2 in each of which cathodes are connected and that are provided in parallel with the feedback resistor VR1, and diodes D3 and D4 that are connected in parallel so that each cathode and each anode are connected and are provided between cathodes of the zener diodes D1 and D2.