To simplify an operation for displaying or hiding windows, depending on a user or usage by the user. An information-processing device, according to the present invention, stores for each window, a time during which the window has been displayed together with another window (simultaneous display time), as a relevance table. The information-processing device, when receiving an instruction to display a window (subject window), refers to a relevance table for the subject window to identify a window whose simultaneous display time is the longest (simultaneous display window), and displays the subject window and the simultaneous display window. Also, the information-processing device, when receiving an instruction to hide a subject window, hides the subject window and a simultaneous display window.