A light-emitting element (2) and a light-receiving element (3) are mounted, spaced from each other, on a main body (1a) of a flexible board (1). These elements (2, 3) are encapsulated in a light-permeable light-emitting side molded resin section (6a, 6b) and a light-permeable light-receiving side molded resin section (6c, 6d), respectively. Positions of the light-emitting element (2) and light-receiving element (3) and orientations of a light-emitting surface of the light-emitting element (2) and a light-receiving surface of the light-receiving element (3) are freely settable owing to flexibility of the flexible board (1). A communication IC (4) is mounted on the flexible board (1) and between the elements (2, 3) and encapsulated in an IC side molded resin section (6e, 6f). An extended portion (1b) extends from a midsection of the main body (1a) of the flexible board (1) and has an external connection terminal (11) at its tip.