A needle selector for a knitting machine which selects a working needle by using a piezoelectric body having piezoelectric element is provided, in which an intermediate position between a rear end portion and front end portion of the piezoelectric body movably supported by a housing is rotatably held by the housing by using a rotary member to stabilize vibration of the piezoelectric body, a sectional structure of the rotary member 3 on a plane which is perpendicular to an axis of the rotary member 3 and perpendicular to a plane of the piezoelectric body is formed such that a bend in a widthwise direction of the piezoelectric body 2 is suppressed to be smaller than a bend in the longitudinal direction, so that a vibration speed and torque of the piezoelectric body further increase and energy saving is achieved.
