Light reception/emission element and sensor device using same

This light reception/emission element (1) is provided with: a semiconductor substrate (2) having one conductivity type; a light-emitting element (3a) having a plurality of semiconductor layers laminated on the upper surface of the semiconductor substrate (2); a light-receiving element (3b) having a reverse-conductivity-type semiconductor region (32) doped with a reverse-conductivity-type impurity on the upper-surface side of the semiconductor substrate (2); and a first electrode pad (33A) disposed on the upper surface of the semiconductor substrate (2), the first electrode pad (33A) representing an electrode of the light-receiving element (3b). The impurity concentration on the semiconductor substrate (2) having one conductivity type is higher in the region immediately under the first electrode pad (33A) than other regions.