There is provided a guide plate for a side air bag. The guide plate includes a fastening member fastened to an inner surface of a vehicle body, a support member bent from a lower end of the fastening member and extending toward a passenger space of a vehicle, and a retaining member extending from a surface of the fastening member toward the passenger space of the vehicle. As the guide plate prevents a side air bag tube from being deployed in an upward direction, force for deploying the side air bag tube is not spread but concentrated to allow the side air bag tube to be properly deployed by opening a head liner.