A photodetector device includes: a first semiconductor region of a first conductivity type electrically connected to a first external electrode: a second semiconductor region of a second conductivity type formed on the first semiconductor region; a third semiconductor region of the first conductivity type formed on the second semiconductor region; and a plurality of fourth semiconductor regions of the second conductivity type formed on the second semiconductor region, each of the plurality of fourth semiconductor regions being surrounded by the third semiconductor region, including a second conductivity type impurity having a concentration higher than a concentration of the second semiconductor region, and electrically connected to a second external electrode.