A resin back door for a vehicle includes a resin inner panel, a resin lower outer panel, a metal left reinforcing member, and a damper stay bracket. The metal left reinforcing member is disposed in a hollow space defined by the inner panel and the lower outer panel, and is fixed to the inner panel with an adhesive leaving a gap. The damper stay bracket is attached on an outer side of the inner panel in a vehicle width direction. In the resin back door for a vehicle, the damper stay bracket is fastened to the left reinforcing member across a collar having one end inserted into a hole provided in the inner panel.