PURPOSE: To attain efficient data transmission reception by counting the number of times of occurrence of a transmission tentative pause state and controlling a receiver side to be an optimum state depending on the result of count.

CONSTITUTION: A clock with a predetermined frequency from a clock generating section 24 is fed to a terminal CK of a communication LSI 12. Moreover, a RAM 26 is a RAM reading/writing reception data or the like under the control of a CPU 11 and made up of a communication buffer and an FDD or the like. The communication buffer is a reception buffer and its capacity is selected so that a free area is in existence by taking the capacity of a sent data file into account. Then the capacity of the communication buffer is controlled variably by the CPU 11 in response to an occurrence rate of a transfer OFF signal indicating a tentative pause signal for data transmission.