A driving method is applied to a solid-state imaging apparatus having photoelectric conversion portions, transfer portion for reading out signal charges, and an excess charge draining portion for draining charges exceeding a saturation charge amount that is set by a reference voltage. One of driving modes is selected from a full pixel mode in which accumulated signal charges are detected individually for each pixel and a pixel mixing mode in which signal charges of a predetermined number of pixels are mixed to be detected. In the full pixel mode, the draining portion is supplied with the reference voltage having the same value during a charge accumulation period and a read transfer period for read transferring charges. In the pixel mixing mode, the draining portion is supplied with the reference voltage having a low level during the charge accumulation period and the reference voltage having a high level during the read transfer period. An appropriate driving for the pixel mixing mode can be performed by avoiding a limitation of a substrate voltage, without deteriorating the spectral characteristics, the sensitivity, nor the linearity.