The rocking mechanism (3) according to the present invention is intended to rock the rocking member with a small force while securing a large rocking angle of the rocking member to be rocked with respect to the base member. (1) The first rocking member (5) supported so as to be rockable about the rocking axis (A) and the first rocking member are disposed at an interval in a direction perpendicular to the first rocking axis The second rocking member (6) supported so as to be rockable about the second rocking axis (B) and the second rocking member are arranged at an interval in a direction orthogonal to the second rocking axis A traction pulley (7) rotatably supported about the rotational axis (C), a fixed pulley (8) rotatably supported about the second swing axis, a fixed pulley and the traction pulley And wire (9) which generates substantially the same direction of tension on both sides of the pulling pulley sandwiching the rotation axis by the applied pulling force With traction pulley, the resultant force of the tension of the wire acting on the axis of rotation, is arranged at a position to generate a moment for swinging the second pivoting member.ベース部材に対して揺動させられる揺動部材の揺動角度を大きく確保しつつ、少ない力で揺動部材を揺動させることを目的として、本発明に係る揺動機構（３）は、第１揺動軸線（Ａ）回りに揺動可能に支持された第１揺動部材（５）と、第１揺動部材に、第１揺動軸線に直交する方向に間隔をあけて配置された第２揺動軸線（Ｂ）回りに揺動可能に支持された第２揺動部材（６）と、第２揺動部材に、第２揺動軸線に直交する方向に間隔をあけて配置された回転軸線（Ｃ）回りに回転可能に支持された牽引プーリ（７）と、第２揺動軸線回りに回転可能に支持された固定プーリ（８）と、固定プーリと牽引プーリとに巻き掛けられ、加えた牽引力によって回転軸線を挟んだ牽引プーリの両側に略同一方向の張力を発生させるワイヤ（９）とを備え、牽引プーリが、回転軸線に作用するワイヤの張力の合力が、第２揺動部材を揺動させるモーメントを発生させる位置に配置されている。
