A solid-state image pickup apparatus includes a reading unit having a plurality of pixels connected thereto, holding signals from the pixels, and a control unit capable of controlling operations of the pixels and reading unit. The control unit controls the pixels and reading unit in a first operation mode without addition, in a second operation mode in which signals from aa of the pixels are added, aa being an integer greater than one, and in a third operation mode in which signals from bb of the pixels are added, bb being an integer greater than aa. The reading unit includes a holding unit having a capacitance value of C, and the holding unit includes a first capacitor having a capacitance value of C/bb and a second capacitor having a capacitance value of C/p, p being a common multiple of aa and bb.