An apparatus for transmitting read data comprises a document reader 101, a data compression unit 102, a data transmission means and a CPU 104. The document reader 101 reads in a document having been subjected to predetermined data processing. The data compression unit 102 performs compression of the read data with a designated file format. The CPU 104 checks the limitation on transmission capacity set in advance for each data transmission means. When the volume of data compressed for transmission falls within the limited range of transmission capacity set for the data transmission means, the read data is transmitted to a destination designated by the user via the data transmission means designated by the user.