On the surface of the peripheral wall portion 2B of the housing 2 is provided with a receiver 7 and the emitter 6. On the surface of the peripheral wall portion 2B of the housing 2, there are provided a blood flow inhibition reduction unit 15 are positioned on the right side of the receiver 7 and the light emitting device 6, the fingertip position is located on the left side of the receiver 7 and the emitter 6 I provide the part 16. When the user is brought into contact with the receiver and the emitter 7 6 the end joint of the finger A F, B Chu-bushi of the finger F is brought into contact with the contact portions 15C of the constriction of blood flow reduction unit 15. Step because occurs between the contact portions 15C and sites around the receiver and 7 light-emitting device 6 in the housing 2, by this step, I will reduce the pressure on the site of the first joint side of the distal segment A of the finger F I can be.筐体2の周壁部2Bの表面には、発光器6および受光器7を設ける。筐体2の周壁部2Bの表面には、発光器6および受光器7の右側に位置して血流阻害低減部15を設けると共に、発光器6および受光器7の左側に位置して指先位置決め部16を設ける。利用者が指Fの末節Aを発光器6および受光器7に接触させると、指Fの中節Bは血流阻害低減部15の接触部15Cに接触する。筐体2における発光器6および受光器7の周囲の部位と接触部15Cとの間には段差が生じるから、この段差によって、指Fの末節Aの第1関節寄りの部位に対する圧迫を低減することができる。
