Provided is a biological sensor capable of reducing stray light that is received without passing through a biological body without increasing the size of the sensor, and capable of improving the reliability of the sensor.A biological sensor includes a circuit board, a light-emitting element and a light-receiving element mounted on a main surface of the circuit board with a predetermined interval therebetween, a light-transmissive light-emitting element sealing portion formed only on an upper portion of a mounting region of the light-emitting element, a light-transmissive light-receiving element sealing portion formed only on an upper portion of a mounting region of the light-receiving element, and a light-blocking portion formed on the main surface of the circuit board and provided in respective peripheries of the light-emitting element sealing portion and the light-receiving element sealing portion and between the light-emitting element sealing portion and the light-receiving element sealing portion.
