A biological sound sensor to be used in contact with a skin of a living body, and includes a casing that has an opening in a face on the side facing the skin of the living body, a double-sided adhesive membrane, one surface of which closes the opening by adhering to the face of the casing and the other surface of which adheres to the skin when collecting a biological sound produced in the living body, and a microphone that is arranged in the casing and picks up the biological sound. The double-sided adhesive membrane includes a one-material portion made from a single type of material across the entire width in the thickness direction, the one-material portion being made from an adhesive material.
