A guide device for guiding a conduit or a medium includes a guide element which delimits a guide channel in which the conduit or the medium is accommodatable and guidable. The guide element has a first layer and a second layer which are disposed one inside the other, are pliable, and delimit a chamber system which is disposed between the first layer and the second layer. The chamber system has a plurality of chambers. The first layer and the second layer are impermeable to a fluid. By acting upon the chamber system with the fluid, the guide element, which is intrinsically pliable, is stiffenable and thereby converted into a rigid state.