PROBLEM TO BE SOLVED: To provide a biological sensor which can measure biological data of a subject with accuracy.SOLUTION: A biological sensor 1 includes: a wiring board 10b an optical sensor part 11 which is provided on a first main surface of the wiring board 10b and includes a light emission part for emitting light to a living body 2 and a light receiving part for detecting intensity of the light passing through the inside of the living body 2 and returning and an adhesive member 10d which is provided on the first main surface of the wiring board 10b in a manner to enclose the periphery of the optical sensor part 11 while providing a space between the optical sensor part 11 and the adhesive member, has adhesiveness and holds the optical sensor part 11, and is attachable to and detachable from the living body 2.It is preferred that: a thickness of the adhesive member 10d is designed to be equal to a thickness of the optical sensor part 11 or lower the adhesive member 10d has a light blocking property and the adhesive member 10d is black in the color.SELECTED DRAWING: Figure 18
