A photodiode array includes a plurality of photodiodes formed in a semiconductor substrate. Each of the photodiodes includes a first semiconductor region of a first conductivity type, a second semiconductor region of the first conductivity type, provided with respect to the first semiconductor region on one surface side of the semiconductor substrate, and having an impurity concentration higher than an impurity concentration of the first semiconductor region, a third semiconductor region of a second conductivity type, provided with respect to the first semiconductor region on the one surface side so as to surround the second semiconductor region separately from the second semiconductor region, and constituting a light detection region together with the first semiconductor region, and a through-electrode provided within a through-hole passing through the first semiconductor region and the second semiconductor region, and electrically connected to the third semiconductor region.