There is provided a hairspring including a main body portion that extends around a central axis along an Archimedes curve; an outer end curve portion that extends along a circumferential direction around the central axis on an outer side in a radial direction from the main body portion; and a reformed portion including a first bent portion that connects the main body portion and the outer end curve portion to each other and is bent outward in the radial direction from a tangent line of the Archimedes curve in a first connection portion with the main body portion, and a second bent portion bent inward in the radial direction from the outer end curve portion in a second connection portion with the outer end curve portion, and in which at least one is curved of the first bent portion and the second bent portion.