PROBLEM TO BE SOLVED: To prevent a mounting part of a tabular member to which a holder holding a control mechanism is mounted, from being exposed in a configuration that the holder is mounted to a seating part by the tabular member.SOLUTION: A seat device comprises: a pressure sensor which measures a measurement relating to a state of a sitting person sitting on a seat; a vibration application device 62 which performs a vibration application operation; an ECU 70 which controls the vibration application device 62 in accordance with a measurement result of the pressure sensor; a holder 80 which holds the ECU 70; and a mounting bracket 90 which is fixed to a lower frame 11d of a seating part 11 for mounting the holder 80 to the lower frame 11d. The mounting bracket 90 includes a mounting projection 91 to which an outer wall 80a of the holder 80 is mounted in a predetermined mounting direction. In a state where the outer wall 80a is mounted to the mounting projection 91, the mounting projection 91 is covered by the outer wall 80a in the mounting direction.SELECTED DRAWING: Figure 10【課題】制御機構を保持する保持器を板状部材によって着座部に取り付ける構成において、保持器が取り付けられる板状部材の取り付け部が露出するのを抑える。【解決手段】シートに着座しているときの着座者の状態に関する計測値を計測する圧力センサと、振動付与動作を行う振動付与装置62と、圧力センサの計測結果に応じて振動付与装置62を制御するECU70と、ECU70を保持する保持器80と、保持器80を着座部11の下部フレーム11dに取り付けるために下部フレーム11dに固定される取り付けブラケット90と、を有し、取り付けブラケット90は、保持器80の外壁80aが所定の取り付け方向において取り付けられる取り付け用突起91を備え、取り付け用突起91に外壁80aが取り付けられた状態では、取り付け用突起91が取り付け方向において外壁80aに覆われている。【選択図】図10