To easily and speedily hold machining material by enlarging the maximum opening width of a holding part.

In this device, holding members 12, 14 longer than the maximum opening width L4 of holding parts 24, 28 are installed on the holding parts 24, 28. The maximum opening width L2 between holding pieces 12B, 14B of the holding members 12, 14 is longer than the maximum opening width L4. This means that machining material 10 even longer than the maximum opening width L4 between the holding parts 24, 28 can be held by the holding pieces 12B, 14B, so removal of a vice device 20 is not necessary, and need of installation work of the machining material 10 using a dial gauge is eliminated. The maximum opening width L2 to hold the machining material 10 by the holding members 12, 14 is therefore enlarged compared to conventional devices, so even the machining material 10 longer than the maximum opening width between the holding parts 24, 28 can be easily and speedily positioned to a table 66 of a milling machine 64, thereby machining work can be smoothly conducted.