There is provided a signal processing device which is capable of suppressing the influence of a digital data process on an analog signal process without completely stopping a digital data processing circuit. A signal, processing device includes an analog signal processing circuit, a digital data processing circuit, a determination section configured to determine an influence of the digital data processing circuit on the analog signal processing circuit, and a control section configured to stop a partial circuit of the digital data processing circuit or lower processing capability thereof in response to a determination result of the determination section.