A slot rod having a plurality of grooves for storing a plurality of optical fibers, a first layer disposed at a center of the slot rod, a second layer provided on an outer peripheral portion of the first layer, a third layer provided on an outer peripheral portion of the second layer, and an outermost layer provided on an outer peripheral portion of the third layer, and the third layer is formed of a material having higher adhesiveness to the outermost layer than a material in a case where the third layer is formed of the same material as the outermost layer.