The present invention provides a back door for an automobile including an inner panel and an outer panel made of resin. A pair of reinforcement metal plates is disposed on an inner wall of the inner panel at end portions in a left-to-right direction of a space formed between the inner panel and the outer panel integrated together. The reinforcement metal plates each include a damper attachment portion to which a damper-connecting member connected to a damper is attached, and a hinge attachment portion to which a hinge extending toward a car body is fixed.