A solid-state image pickup device includes an adder adding signals from pixels to achieve a high S/N, while performing both static image and moving image pickup. The device has a pixel unit having pixels arranged two-dimensionally and outputs pixel signals derived by photoelectric conversion. The device operates in a first mode of reading a pixel signal of every pixel, and a second mode of adding and reading a plurality of pixel signals. Variable gain column amplifiers perform readout at different gains in the first and second modes. The device also has output lines where output signals from the pixels arranged in one line are outputted respectively, and at least one of the variable gain amplifier is connected to each of the output lines. The gain at the time of readout in the second mode is higher than the gain at the time of readout in the first mode.