PROBLEM TO BE SOLVED: To provide a biological information detector and the like which can suppress negative effects caused by a contact state between a subject and a contact surface and can suppress negative effects by direct light from a light emitting part.SOLUTION: A biological information detector includes: a detecting part which has a light receiving part 140 for receiving light from a subject and a light emitting part 150 for emitting light to the subject a translucent member 30 which is provided at a case surface side that comes in contact with the subject of the biological information detector and transmits the light from the subject and light from the light emitting part 150 diaphragm parts 80 and 82 which are provided between the translucent member 30 and the detecting part, between the translucent member 30 and the subject, or in the translucent member 30 and narrow the light from the subject and light from the light emitting part 150 in an optical path between the subject and the detecting part and a light shielding part 100 provided between the light receiving part 140 and the light emitting part 150.
