biological sensor (100), wiring the main surface of the substrate (160) (160a) in the arranged light-emitting elements (121, 122) and the light receiving element (123), a light-shielding portion provided between the light-emitting element sealing portion (171) and the light receiving element sealing part (172) (173), the light blocking Part (173) through the wiring board (160) with a substrate having a light transmitting property provided in parallel with the (150), the light-emitting element sealing part (171), a light receiving element sealing part (172) and light shielding part ( It comprises 173) and the substrate (150) and the adhesive layer having a light-transmitting property for bonding the (180), a first ECG electrode attached to the main surface (150a) of the base (150) (130). Refractive index of the substrate (150) is set higher than the refractive index of the adhesive layer (180), and the base of the first ECG electrode (130) (150) side surface (130a) includes a base ( stray light passing through the 150) is formed as roughened scattered.生体センサ(100)は、配線基板(160)の主面(160a)に配置された発光素子(121,122)及び受光素子(123)と、発光素子封止部(171)と受光素子封止部(172)との間に設けられる遮光部(173)と、遮光部(173)を介して配線基板(160)と平行に設けられる透光性を有する基材(150)と、発光素子封止部(171)、受光素子封止部(172)及び遮光部(173)と基材(150)とを接着する透光性を有する接着層(180)と、基材(150)の主面(150a)に取り付けられる第1の心電電極(130)を備える。基材(150)の屈折率は接着層(180)の屈折率より高く設定され、かつ、第1の心電電極(130)の基材(150)側の面(130a)は、基材(150)の中を通る迷光が散乱されるように粗く形成されている。
