As a server computer receives, in a communication portion, data on an appearance of a custom-made product, such as a stamp, from a purchaser computer, a preview image creating portion creates smaller-sized preview image data than normal image data to be used when a stamp is produced by a stamp producing device connected to a supplier computer. The created preview image data is transmitted from the communication portion to the purchaser computer and the supplier computer, as required, and displayed on respective browsers. Therefore, the purchaser of the custom-made product can be promptly view the preview image of the custom-made product.