A control terminal device for controlling through a network a plurality of communication devices (11, 12, 13, 14) disposed in respective areas and mutually connected via the network, the control terminal device comprising: a communication section for transmitting command messages to the plurality of communication devices (11, 12, 13, 14); a display section for displaying an operation screen; and a display control section controlling the display section to display a device selection screen for selecting any one of the plurality of communication devices (11, 12, 13, 14), wherein the display control section displays area images indicating the areas in which the respective communication devices are disposed so as to serve as a selection operation section for selecting the respective communication devices on the device selection screen; wherein when any one of the area images is selected, the display control section displays, instead of the device selection screen, a source selection screen for selecting an audio source that can be reproduced by the audio device disposed in the selected area; wherein the source selection screen includes a source selection operation section corresponding to one or each of a plurality of audio sources, and the selected area image indicating the area serves as a background of the source selection screen; wherein the display control section causes the display section to further display group setting screens for selecting a master device by which an audio source is selected on the source selection screen and for selecting a slave device that receives the sound of the audio source selected by the master device via the network and synchronously reproduce the sound; and wherein when the group setting is performed, the display returns from the group setting screen to the device selection screen and the display control section changes a display mode of the area image corresponding to the master device on the device selection screen by displaying the names of the slave areas on the area selection image of the area corresponding to the master device and causes the display images to be blurred and the display images of the slave areas cannot be selected. a communication section for transmitting command messages to the plurality of communication devices (11, 12, 13, 14); a display section for displaying an operation screen; and a display control section controlling the display section to display a device selection screen for selecting any one of the plurality of communication devices (11, 12, 13, 14), wherein the display control section displays area images indicating the areas in which the respective communication devices are disposed so as to serve as a selection operation section for selecting the respective communication devices on the device selection screen; wherein when any one of the area images is selected, the display control section displays, instead of the device selection screen, a source selection screen for selecting an audio source that can be reproduced by the audio device disposed in the selected area; wherein the source selection screen includes a source selection operation section corresponding to one or each of a plurality of audio sources, and the selected area image indicating the area serves as a background of the source selection screen; wherein the display control section causes the display section to further display group setting screens for selecting a master device by which an audio source is selected on the source selection screen and for selecting a slave device that receives the sound of the audio source selected by the master device via the network and synchronously reproduce the sound; and wherein when the group setting is performed, the display returns from the group setting screen to the device selection screen and the display control section changes a display mode of the area image corresponding to the master device on the device selection screen by displaying the names of the slave areas on the area selection image of the area corresponding to the master device and causes the display images to be blurred and the display images of the slave areas cannot be selected.