To provide a fixture and a sealing tool capable of being attached and detached by the easy operation, capable of reliably performing fixing and sealing, and capable of being used for a stopper of a bottle or the like.

A silicone rubber-made cylindrical elastic film 45 having its lower edge fixed to a flange part 44 formed on the tip of a shaft body 43 and its upper edge fixed to the lower surface of a base body 41 is provided on the periphery, projecting from the lower surface of the base body 41, of the inverted T-shaped sectional shaft body 43 vertically movably inserted in a shaft hole 42 through which the approximately cylindrical base body 41 is to be inserted. The upper end of the shaft body 43 is inserted in a cylindrical slide cylinder 46 slidably inserted in the shaft hole 42 in the loosely fitted state and fixed to the slide cylinder 46 by a screw 47. A coil spring 51 for upward energizing the shaft body 43 to make the flange part 44 approach the lower surface of the base body 41 and for outward projecting the cylindrical elastic film 45 is provided around the shaft body 43 between the upper bottom surface of the slide cylinder 46 and a washer 50 attached to a step part 49 in the lower end opening part of the shaft hole 42 of the base body 41 and also in a clearance 48 between the slide cylinder 46 and the shaft body 43. A step part 52 to be locked on the opening edge of a bottle is formed on the intermediate part of the base body 41, a flange part 53 is formed on the upper end periphery of the base body 41, and a cap 54 is attached on the upper end of the slide cylinder 46 projected upward from the base body 41.