A step device for a vehicle includes a movable step supported under a door opening, and a coupling member supported by a sliding door that opens and closes in a vehicle front-rear direction with a shifting zone in a vehicle width direction. The movable step is provided with a guide rail that opens downward and extends in the vehicle front-rear direction. The coupling member includes: a fixed member fixed to the sliding door; an arm member coupled to the fixed member; a guide roller disposed inside the guide rail; and an urging member configured to apply to the arm member an urging force in a direction in which the guide roller turns upward.