To provide a communication apparatus capable of maintaining line closure with optimum voltage current characteristics even if power supply conditions of a line change are changed.

When dial send-out processing is performed in addition to line closing processing and power supply conditions of the line voltage may be changed, a voltage current adjustment start instruction is sent out to start voltage current adjustment processing. Consequently, the line voltage and line current are adjusted in accordance with new conditions of power supply. Furthermore, the voltage current adjustment processing ends with a lapse of a predetermined time after the voltage current adjustment start instruction. Consequently, the line voltage is prevented from being oscillated.