PROBLEM TO BE SOLVED: To provide a synthetic fiber for self-healing of a crack of a cement hardened body, which accelerates self-healing of the crack of the cement hardened body, the cement hardened body including the synthetic fiber, and a method for repairing the crack of the cement hardened body.SOLUTION: A synthetic fiber for self-healing of a crack of a cement hardened body has a noncircular cross section. One or more resins selected from a group consisting of a polyolefin-based resin and a polyacetal resin occupy at least a part of a fiber surface, and the noncircular cross section has two or more protrusions. The cement hardened body includes the synthetic fiber for self-healing of the crack of the cement hardened body and cement. The invention is also related to a method for repairing the crack of the cement hardened body, in which the crack is self-healed by intermittently or continuously imparting water to the cracked part of the cement hardened body including the synthetic fiber for self-healing of
