A joint power generating device (8) has a multilayer structure constituted by alternately stacking an elastic member (41), which incorporates a hermetically sealed air chamber, and a partition plate (42) with high stiffness, an elastic structure (31), which has a through hole (43) formed therein, and a flexible lengthy member (32) inserted in the through hole (43). The joint power generating device (8) is configured to transmit a force between the lengthy member (32) and the elastic structure (31) such that the force for compressing the elastic structure (31) increases as the tension on the lengthy member (32) increases.
