An elongated member which is deflectable and hollow and which is configured for deflection that follows the shape of a biological organ for smooth movement within the organ. The elongated member includes: an operating member configured to deflect the elongated member or deform the elongated member into a linear state and a deflection mechanism at least including a guide portion having a grooved portion formed thereon, an engaging portion engageable with the grooved portion and a supporting portion configured to support the engaging portion for relative movement on the guide portion a gap being formed between the guide portion and the engaging portion so as to allow movement of the engaging portion in the grooved portion.
