There is provided a flexibility/rigidity adjustable apparatus which can change over its state between a flexible state in which such apparatus is freely bendable and a rigid state in which such bending is restricted when in use. A flexible closing cover 18 which can expand/shrink is provided on an outer circumference 2 of a flexible tube 1. A latching member 7 which moves together with the closing cover 18 is provided, and a latching-member receiving part 11 with which the latching member 7 can engage is provided at the outer circumference 2 of the tube 1. A closed space 21 formed between the closing cover 18 and the tube 1 is connected to an air inlet/outlet part 22. As the air is evacuated through the inlet/outlet part 22 to change the pressurized condition of the closed space 21 from an atmospheric pressure condition to a negative pressure condition, the closing cover 18 reduces its diameter around an axis 4, and the latching member 7 is caused to engage with the latching-member receiving part 11. As air is supplied in the closed space 21 to make the interior thereof in an atmospheric pressure condition, the closing cover 18 expands, and engagement of latching member 7 with the latching-member receiving part 11 is released, so that the tube 1 becomes a flexible state from a rigid state.
