A solid-state image pickup apparatus selects, in a first image pickup circumstance in which dark current is liable to occur in vertical transfer paths of an array of photo-sensors, a first transfer mode in which the potential well capacity in the vertical transfer paths is relatively small, and, in a second image pickup circumstance in which the dark current is small in quantity, a second transfer mode which is greater in potential well capacity than the first transfer mode. As a positive voltage applied to the read-out gates of the photo-sensors, a first voltage mode indicating a relatively low positive voltage that suppresses impact ionization is set in the first image pickup circumstance, and, a second voltage mode indicating a positive voltage higher than in the first voltage mode is set in the second image pickup circumstance so as to cause the impact ionization.