An electronic device for displaying video signals on a display device has a processing device and a storage device. The processing device generates a user interface including video areas for showing the video signals on the display device. The processing device determines a first area size for the video areas based on an interface size of the user interface, a row quantity and an aspect ratio, to arrange the video areas. The processing device adjusts the first area size to generate a second area size and a third area size for the video areas according to the interface size, when the number of the video areas in each row is not equal to each other. The processing device shows the video signals in the video areas based on the second area size and the third area size on the user interface of the display device.