CHAIR HAVING VERTICALLY MOVABLE SEAT PART

PROBLEM TO BE SOLVED: To provide a chair having a vertically movable seat part, including a support base part supporting the seat part, elevation drive means of the seat part, and a descent failure detection sensor existing on the lower face of the seat part and detecting an object to be detected by swing movement, in which the elevation drive means is stopped by the detection of the sensor, the chair allowing the object to be detected in the front and the back of the seat part to be detected to stop the elevation drive means.SOLUTION: In a chair having a vertically movable seat part 2, a descent failure detection sensor 6 includes a movable member 60 supported by the lower face of the seat part 2, and sensor switches detecting displacement of the member 60. The movable member 60 is suspended at suspension supporting points 62a-62d positioned corresponding to corner parts of a virtual quadrangle covering the lower face of the seat part 2 and can move upward and can swing in all directions. The two sensor switches are disposed opposite to each other in the center between the suspension supporting points arranged side by side and detect central displacement between the suspension supporting points due to the upward movement or the swing of the movable member 60, and when one or both of the two sensor switches detect the displacement, elevation drive means 5 is stopped.