An image sensor according to an embodiment may include a plurality of pixels. Each pixel of the plurality of pixels may include first, second, third and fourth photodiodes configured to convert light into an electric signal, and an electric circuit configured to add at least two of the electrical signals converted respectively by the first, second, third and fourth photodiodes and then output the added signals. An electronic device according to an embodiment may include the image sensor. The image sensor and the electronic device may offer an auto focusing function by controlling signals converted by and outputted from the plurality of photodiodes. Other various embodiments are possible.