A communication apparatus having a temporary managing portion for controlling a temporary memory, a main managing portion for controlling a main memory and an operation control portion. The operation control portion is operative to cause the temporary managing portion and the main managing portion to determine the amount of reception at intervals of predetermined time and the amount of transmission at intervals of the determined time, to store comparative result data representing the result of comparison between the amount of reception and the amount of transmission in the temporary memory or the main memory, and to find an excessive input state, an excessive output state or a balanced input/output state on the basis of an excessive input communication signal reception state, an excessive output communication signal transmission state and a balanced input communication signal reception/output communication signal transmission state recognized based on the comparative result data, and operative to cause an input communication signal reception and an output communication signal transmission to be restrained in response to the found excessive input state, excessive output state or balanced input/output state.