An image pickup apparatus includes a pixel array including a plurality of pixels arranged in a plurality of rows and a plurality of columns, and a plurality of column signal processing circuits provided respectively for the columns of the pixel array, each being configured to receive output signals from the pixels and an analog signal varying with time. The plurality of column signal processing circuits include a first column signal processing circuit and a second column signal processing circuit configured such that each of the first column signal processing circuit and the second column signal processing circuit is configured to be independently switched between a driving state and a power saving state. A signal line for supplying the analog signal to the first column signal processing circuit and a signal line for supplying the analog signal to the second column signal processing circuit are electrically isolated from each other.