Solid-state image pickup device and processing method, with A/D conversion on pixel signals read from a pixel array part that effectively achieves reductions in power consumption, size and price while retaining a high-quality image output. The device includes a pixel array part, a CDS (correlated double sampling) circuit, and an A/D converter. A pixel signal read via a signal line is subjected to noise elimination processing in the CDS circuit, and is then inputted into the A/D converter. The A/D converter includes a ΔΣ modulator and a digital filter to perform highly accurate A/D conversion. The A/D converter can also be provided at the front stage of the CDS circuit.