An amplifier including a first cascode circuit including a first transistor and a second transistor whose source or emitter is coupled to a drain or a collector of the first transistor, a second cascode circuit being a differential pair with the first cascode circuit, the second cascode circuit including a third transistor whose source or emitter is coupled to a source or an emitter of the first transistor and a fourth transistor whose source or emitter is coupled to a drain or collector of the third transistor, a first feedback path that couples between an output terminal of the third transistor and an input terminal of the first transistor, the first feedback path including a first capacitative element, and a second feedback path that couples between an output terminal of the first transistor and an input terminal of the third transistor, the second feedback path including a second capacitative element.