A muscle contraction detection sensor for detecting a muscle contraction that includes: a substrate to be mounted facing a muscle to be detected； at least two pressing members that are disposed on the substrate and are to be pressed against the muscle； and at least two reaction force detection units configured to detect respective reaction forces received by the pressing members, wherein the pressing members include a first pressing member and a second pressing member, the reaction force detection units include a first reaction force detection unit and a second reaction force detection unit, a muscle contraction is detected based on a change in a difference between, or a change in ratios of, the reaction force received by the first pressing member detected by the first reaction force detection unit and the reaction force received by the second pressing member detected by the second reaction force detection unit.
