Solid state imaging device, method of driving solid state imaging device and image pickup apparatus

When an addition/averaging process is done for pixels in the same color in a unit pixel block in a stage reading pixel information to a horizontal signal line, the addition/averaging process is also done for a noise component added in a signal process from the pixels to the horizontal signal line. Thus, a problem arises in the signal-to-noise ratio. Each of signal processing circuits of a column signal processing circuit part is provided with reverse amplifiers which output signals of pixels transmitted by a vertical signal line at a low impedance, and with feedback capacitances which are adjustably connected in parallel to these reverse amplifiers, the signal processing circuit being disposed at every column. These feedback capacitances are used to do row wise and column wise pixel addition for the pixels in the same color in the unit pixel block to take out pixel signals for a single pixel in simulation.