To provide a shaft which allows a smooth and reliable contraction operation by ensuring that an engaging pin certainly juts our from the hole on an inner pipe, when the shaft is contracted.

A plate spring 18 is used for an energizing member for an engaging pin 16. An outer pipe 11 and an inner pipe 12 have an elliptic cross section. A straight portion 11A and 12A are arranged in the direction of the major axes of the cross sections so that the engaging pin 16 can closely contact with the inside surface of the inner pipe 12. Namely, the distal end side of the plate spring 18 makes a surface contact with he inside surface of the inner pipe 12 in a wide contact area. The plate spring 18 always moves and stays along the longitudinal direction of the inner pipe 12 during the adjustment of a shaft 13. The engaging pin 16 energized by the plate spring 18 certainly juts our from the inside of a small hole 15 of the inner pipe 12.