Provided is a technique of calculating a proper margin according to the area or a radio propagation estimation method in the area design of wireless communication using a radio propagation simulator. From a storage part wherein information relating to positions where deterioration of a communication quality or a radio quality is confirmed and information relating to the radio conditions at the positions are associated with each other, a margin design system extracts positions where the radio conditions are equal, estimates the radio quality at the positions by the radio propagation simulator, and calculates the margin of a radio quality estimated value on the basis of the estimated radio quality.