1. A mobile terminal, comprising: a touchscreen; and a controller configured to: display a playing image of a first video as a main image in a first region of the touchscreen, display a video list in a second region of the touchscreen different than the first region while the playing image of the first video is displayed in the first region, the video list comprising a first thumbnail image representing the first video and a second thumbnail image representing a second video, display a playing image of the second video in a first size as a preview image in the second region in a sub playing window while the playing image of the first video is displayed in the first region, in response to a first proximity touch input to the second thumbnail image, wherein the playing image of the first video in the first region and the playing image of the second video in the sub playing window in the second region are concurrently displayed in response to the first proximity touch input to the second thumbnail image, display the playing image of the second video in a second size larger than the first size, in response to a first contact touch input to the second thumbnail image, and display a first progress bar for the first video and a second progress bar for the second video while the first image is played back as the main image, wherein a first sub image of the first video is displayed with respect to the first progress bar and a second sub image of the second video is displayed with respect to the second progress bar, and wherein the first progress bar for the first video, the first sub image of the first video, the second progress bar for the second video, and the second sub image of the second video are concurrently displayed while the first image is played back as the main image.