A thin client system transmits screen data including one or more windows operated in a server apparatus to a client apparatus, and displays the screen data in the client apparatus. The system includes a list display section, a selection information transmitting section, and an active state setting section. The list display section displays, in the client apparatus, a list of window names of the windows operated in the server apparatus, in response to a list display instruction operation by the user. The selection information transmitting section transmits information that a desired window is selected, when a name of the desired window is selected by the user among the window names displayed by the list display section. The active state setting section renders a window corresponding to the information active in the server apparatus, when the information that the window is selected is transmitted by the selection information transmitting section.