A biological sensor includes: a first sheet that has flexibility and/or stretchability and a second sheet that has flexibility and/or stretchability. The second sheet has a first surface facing the first sheet, and a second surface opposite to the first surface. The second surface has a plurality of projections that are configured to be brought into contact with a living body to obtain information on the living body. In the second surface, at least part of each of the plurality of projections has conductivity. In the first surface, a portion surrounding each of the plurality of projections is bonded to the first sheet. Within each of the plurality of projections, an enclosed space defined by the first surface of the second sheet and the first sheet is present
