A flexible printed circuit board includes: a trunk portion; and a pair of branch portions as two portions branched from the trunk portion and arranged on a battery including multiple arrayed cells, in which for at least one branch portion of the pair of branch portions, bending is performed using a pair of parallel bending lines extending apart from the other branch portion as extending apart from the trunk portion, and the at least one branch portion is bent such that a direction of bending at one bending line of the pair of parallel bending lines and a direction of bending at the other bending line are directions opposite to each other.