A metal sheet has a longitudinal direction and a width direction. The metal sheet has shapes in the width direction that are taken at different positions in the longitudinal direction of the metal sheet and differ from one another. Each of the shapes is an undulated shape including protrusions and depressions repeating in the width direction of the metal sheet. A length in the width direction of a surface of the metal sheet is a surface distance. A minimum value of surface distances at different positions in the longitudinal direction of the metal sheet is a minimum surface distance. A ratio of a difference between a surface distance and the minimum surface distance to the minimum surface distance is an elongation difference ratio in the width direction. A maximum value of elongation difference ratios is less than or equal to 2×10−5.