A linear extension and retraction mechanism includes a plurality of flat-plate shaped first pieces that are connected to each other, and a plurality of second pieces having a cross-sectional U-shaped groove frame shape that are connected to each other. A leading first piece of the plurality of first pieces and a leading second piece of the plurality of second pieces are joined by a head section. The first and second pieces become linearly rigid when the first pieces are joined to an upper part of the second pieces, and the first and second pieces return to a bent state when separated from each other. Protrusion sections that protrude inward are extended in the width direction in a bottom plate of each second piece. Corners of edge parts of the protrusion sections are chamfered.