To estimate the generating area of wind around building with ease and in a short time.

A data base 6 holds position data expressing a position where a wind of higher speed than an original wind is generated near a building when a wind is blown to the building by making respectively correspond to the dimension of the building and the direction of the wind. An input means 4 generates each data of the dimension of the building and the direction of the wind based on a prescribed operation when the prescribed operation is executed for inputting the dimension of the building and the direction of the wind. A retrieving means 8 retrieves the data base 6 based on data on the dimension of the building and the direction of the wind generated by the data input means 4 to extract position data. A correction means 10 corrects position data obtained by the retrieving means 8 based on data on the dimension of the building coordinated with position data extracted by the retrieving means 8 by the data base 6 and data on the dimension of the building generated by the data input means 4. An output means 12 prepares a drawing of wind speed-increasing areas based on this corrected position data and outputs it.