A muscle supporter includes a sheet member that is to be closely attached to skin covering a muscle, a muscle strength condition detector, a muscle contraction timing detector, and a muscle assist movement provider. The muscle strength condition detector disposed on the sheet member detects information related to muscle strength condition of the muscle. The muscle contraction timing detector disposed on the sheet member, in operation, detects a muscle contraction timing of the muscle. The muscle assist movement provider disposed on the sheet member, in operation, assists the muscle to contract in response to the detected information and the detected muscle contraction timing.