A MOS-type solid-state image pickup device includes a photoelectric conversion unit having a first semiconductor region of a first conductivity type, a second semiconductor region of a second conductivity type forming a pn-junction with the first semiconductor region, a third semiconductor region of the first conductivity type disposed at a light incident side of the second semiconductor region, and a transfer MOS transistor having the second semiconductor region, a fourth semiconductor region of the second conductivity type, and a gate electrode disposed on an insulating film on the first semiconductor region between the photoelectric conversion unit and the fourth semiconductor region to transfer a charge carrier from the second semiconductor region to the fourth semiconductor region. The photoelectric conversion unit and the transfer MOS transistor are disposed on a substrate. A fifth semiconductor region of the second conductivity type is arranged continuously to the second semiconductor region under the gate electrode, and a sixth semiconductor region of the second conductivity type having an impurity concentration lower than that of the fourth semiconductor region is arranged at a side of the gate electrode in the fourth semiconductor region. A drain of the transfer MOS transistor includes the fourth and sixth semiconductor regions, and a bias is applied to the drain, and the fifth semiconductor region is depleted during reading out the charge carrier from the second semiconductor region.