PURPOSE: To obtain a flexible conduit capable of being used with safety even in the presence of a large differential pressure between the inside and outside by covering the outside of a flexible conduit composed of a bellows with an envelope made of resilient material, and charging a vibration damping member between the envelope and the bellows.

CONSTITUTION: A flexible conduit includes an envelope 2 made of a resilient material provided on the outside of a bellows 1, and a vibration damping material 3 in a space between the envelope 2 and the bellows 1. One end of the flexible conduit is connected to a vacuum equipment, and a flange provided on the other end is connected to a vacuum pump. Thus, the vacuum equipment is held in a vacuum state, and consequently, there occurs a differential pressure between the inside and outside of the bellows 1 which causes the gill of the bellows 1 to be elastically deformed thereby generating expansible force in the axial direction. The vibration damping material 3 includes a gel-like urethane resin with a low elasticity or the like. Therefore, ir is possible to obtain the flexible conduit capable of used with easy and safety even in the increased differential pressure between the inside and outside of the flexible conduit.