A seat apparatus for a vehicle includes a side support portion moved in first and second directions, a driving device moving the side support portion in the first direction and in the second direction, a vehicle location obtaining means for obtaining vehicle location information including a present location of the vehicle, a curve information preliminarily obtaining means for preliminarily obtaining curve information on a map data including a curve starting point located in an area existing a first predetermined distance ahead from the present location of the vehicle, a control starting point determining means for determining a point existing a second predetermined distance closer to the vehicle than the curve starting point as a control starting point, a control starting point memorizing means for memorizing the control starting point, and a drive control means for starting control on the driving device when the vehicle reaches the control starting point.