To make a vacuum maintainable even on a small irregular surface, by providing a negative pressure chamber, elastic cylindrical seal material in an opening part peripheral edge of the negative pressure chamber, and an annular sheet-state slip material affixed to a top surface of the cylindrical seal material to warp internal/external peripheral edges from a running surface.

A board 21 is provided with a negative pressure chamber 23 opened to a suction surface side, a hole 24 is drilled in a back surface thereof and connected to a vacuum device, an annular groove 22 opened to the suction surface side is provided in an external peripheral edge of the negative pressure chamber 23, and an annular seal material 12 of slide member is fit inserted to this annular groove 22. The seal material 12 consists of flexible material of sponge rubber or the like, to surround the periphery of the negative pressure chamber 23, and a slip material 11 of Teflon or the like is affixed to an opening end of the seal material 12. The slip material 11 is formed in shape with an internal diametric side circular and an external diametric side protruding two sheets of petals, so as to warp the internal diametric side and the petals from a running surface, and this thickness is formed as thin as possible. In this way, the slide member 10 elastically corresponds to irregularity of a suction surface, air-tightness in a vacuum chamber can be maintained, and the slip material 11 of small friction coefficient, generating small resistance force at moving time, can be smoothly moved.