A bending mechanism includes: a support member; a pivoting member supported at a distal end of the support member to be pivotable about an axis intersecting the longitudinal axis of the support member; a link disposed along the longitudinal axis and transmitting a force applied at a proximal end thereof to cause the pivoting member to pivot; and an adjuster adjusting stresses in the link so as not to exceed a threshold, at each pivoting position of the pivoting member with respect to the support member. The link includes a first member connected to the pivoting member and a second member disposed closer to the proximal end than the first member is. The adjuster includes a movable member moving in predetermined direction when the first and second members are relatively moved, and a spring biasing the movable member in such direction as to prevent the movement of the movable member.