A solid-state image sensor including a pixel array portion formed from a two-dimensional array of ordinary imaging pixels each having a photoelectric conversion unit and configured to output an electric signal obtained through photoelectric conversion as a pixel signal, and focus detection pixels for detecting focus. The focus detection pixels include at least a first focus detection pixel and a second focus detection pixel each having a photoelectric conversion unit and configured to transfer and output an electric signal obtained through photoelectric conversion to an output node. The first focus detection pixel and the second focus detection pixel share the output node. The first focus detection pixel includes a first photoelectric conversion unit, and a first transfer gate for reading out an electron generated through photoelectric conversion in the first photoelectric conversion unit to the shared output node.