To provide a slide door device for a vehicle in which a treading load is hardly transmitted to a road roller.SOLUTION: A slide door device 30 is provided with a lower roller unit 21 as a guide roller unit 20 extending between a slide door 4 and a vehicle body 2 to engage a guide roller with a guide rail 10 provided in the vehicle body 2 by being fixed to the slide door 4 and bring a road roller 35 into slide contact with a sliding surface S provided in the vehicle body 2. Also, the slide door device 30 is provided with a pressure receiving member 60 to which a treading load F of an occupant getting on and off a vehicle is applied through a door opening part provided with the slide door 4 by moving together with the slide door 4 in an opening/closing operation direction of the slide door 4 to extend between the vehicle body 2 and the slide door 4. Then, the slide door device 30 is provided with a load transmission member 65 for forming a transmission path of the treading load F to the vehicle body 2 bypassing the road roller 35.SELECTED DRAWING: Figure 7