Tension control device and tension control system

A tension control device (100) is provided with: a first mechanical loss coefficient estimation unit that estimates a mechanical loss coefficient that varies according to the winding diameter of a foil material (5) wound around a roll shaft (6), which is a rotating body, on the basis of the tension of the foil material (5) wound around the roll shaft (6) and wound or unwound by the rotation of the roll shaft (6) when the roll shaft (6) rotates, and the winding diameter of the foil material (5) wound around the roll shaft (6); and a calculation unit that performs correction using a mechanical loss coefficient that varies according to the winding diameter, and generates a control command for rotating the roll shaft (6). 张力控制装置(100)具有：第1机械损失系数推定部，其基于作为旋转体的辊轴(6)旋转时的卷绕于辊轴(6)、通过辊轴(6)的旋转而卷绕或者绕出的箔材材料(5)的张力和卷绕于辊轴(6)的箔材材料(5)的卷径，对根据卷径而变化的机械损失系数进行推定；以及运算部，其进行使用了根据卷径而变化的机械损失系数的校正，生成使辊轴(6)旋转的控制指令。