A structure of operation portion of height adjuster of vehicle seat is provided, in which a brake unit associated with the height adjuster and a support element on which a control lever is mounted are disposed. Further, a transmission mechanism of parallel linkage structure with four articulation points is operatively connected between the bake unit and support element. According thereto, the control lever has operative connection with the brake unit via four articulation points of three link members, such that two of the link members are pivotally connected with the respective brake unit and support element, maintaining parallel relation with each other, while other remaining one of the link members is pivotally connected between those two link members.