Abstract: Image data communicating apparatus and communication data quantity adjusting method in an image data communication system suitable for use when image data is transferred in a network environment. Image data is transferred in a most suitable quantity based on traffic of a network to avoid an effect on other services provided by the network. The apparatus has a data transmitting unit for transmitting image data to another image data communicating apparatus, a traffic detecting unit for detecting traffic of the network, and a communication data quantity adjusting unit for initially setting a transmittable number of image transferring frames on the basis of the detected traffic, and for automatically adjusting the quantity of data communication in the data transmitting unit on the basis of changing traffic on the network by altering the set number of frames.