The present invention provides a method for monitoring another video source in addition to a current video source. One method according to the present invention comprises outputting a first video signal provided from a first contents source (for example, a broadcasting channel) and displaying a video from a second video signal provided from a second contents source intermittently with a video from the first video signal on a single screen. During the displaying, a multi-view displaying operation, in which the video from the second video signal is displayed together with the video from the first video signal on the single screen for a first time period, and a single-view displaying operation, in which the video from the first video signal is displayed alone on the single screen for a second time period longer than the first time period, are repeated in an alternate manner.