The present invention discloses a collapsible side panel structure of a roof panel, set upon the outermost rod of the roof panel and includes at least one first base unit; at least one second base unit; a fastener; and a side panel. With the implementation of the present invention, the side panel can be raised and fixed securely to contain and protect small objects or luggage, or the side panel can be set flat on the roof panel and fixed securely to contain larger or wider objects. Together with the invention of the axis deviation between the rotation axis of the side panel and the axis of the first and second through holes, the side panel can be really set flat on or set vertically standing on the roof panel.