Abstract: A support structure for a collapsible shelter, includes legs and upper beams hinged together. Each upper beam is composed of two component rods connected with each other by a freely swinging hinge. Each leg has a sliding part thereon. There is provided an upper or upward stay bar between the sliding part on each leg and the component rods of the upper beam respectively. Both end connections of the top stay bar are freely swinging hinges. The leg has also a stop means thereon to limit motion of the sliding part in outspread state. The support structure does not need to be assembled and dismantled each time when it is to be used and can be easily and quickly spread out and collapsed, saving both time and manpower.