A communication device includes a communication unit configured to send and receive data via an attachable and detachable line, a power controller configured to reduce a power supply to the communication unit when a certain condition is satisfied, and a determination unit configured to determine whether or not a setting for sending and receiving data via the line by the communication unit is made. The power controller maintains the power supply to the communication unit at a call-receivable level, if it is determined that the setting for using the line is made.