Provided is a bending and extending device that has a structure advantageous for preventing unexpected local bending due to buckling. This bending and extending device 1 comprises a guide unit 2 that is elastic and is hollow, and a movable part 3 that is inserted into the guide unit 2 so as to move freely. The movable part 3 comprises a plurality of strip-shaped flexible parts 30a, 30b that extend in the axial direction of the guide unit 2, and the distal ends of the flexible parts 30a, 30b are joined together. In this bending and extending device 1, in a case where a cross section is formed in which, by way of slide operation of the flexible parts 30a, 30b, a contact point T between the flexible part 30a and the inner face of the guide unit 2 is present on an extension line Y of a line segment connecting the centroid P of the flexible part 30b and the axial center G of the guide unit 2 and the flexible parts 30a, 30b are in contact, the centroid P of the flexible part 30b is not positioned in the area in which the contact point T is present when the cross section is divided into two areas with a prescribed straight line X, where the prescribed straight line X is a straight line that passes through the axial center G of the guide unit 2 and is orthogonal to the extension line Y.Linvention concerne un dispositif de pliage et dallongement qui a une structure avantageuse pour empêcher une flexion locale inattendue due au flambage. Ce dispositif de pliage et dallongement 1 comprend une unité de guidage 2 qui est élastique et est creuse, et une partie mobile 3 qui est insérée dans lunité de guidage 2 de façon à se déplacer librement. La partie mobile 3 comprend une pluralité de parties flexibles 30a, 30b en forme de bande qui sétendent dans la direction axiale de lunité de guidage 2, et les extrémités distales des parties flexibles 30a, 30b sont jointes lune à lautre. Dans ce dispositif de pliage et dallongement 1, dans un cas où une section transversale est formée dans
