PROBLEM TO BE SOLVED: To provide a biological information detector and the like which can suppress degradation in quality of a detection signal by pressure fluctuation or the like.SOLUTION: A biological information detector includes: a detecting part having a light receiving part for receiving light from a subject a translucent member 30 which is provided at a case surface 22 side that comes in contact with the subject of the biological information detector, transmits light from the subject, and has a projection part 40 that comes in contact with the subject and presses it when measuring biological information about the subject and a pressure suppressing part 60 which is provided so as to encircle the projection part 40 on the case surface 22 and suppresses pressure the projection part 40 gives to the subject. In a planar view from the direction orthogonal to the case surface 22, the pressure suppressing part 60 has a pressure suppressing surface 62 extending in a second direction DR2 orthogonal to a first direction DR1 to be a circumferential length direction of the subjects part to be detected.
