A mobile terminal device comprising: a display unit; a near field wireless communication unit configured to perform near field wireless communication with a printer within a communicable distance from the printer; and a controller configured to: control the display unit to display a first screen configured to show one or more image data sets each containing one or more pieces of image data and accept a selection of a data set with multiple images from the one or more image data sets; control the display unit to display a preview button wherein, in response to a tapping operation of the preview button, the display unit displays, on a preview screen, one or more images corresponding to the one or more pieces of image data contained in the selected image data set by displaying an intended image of the one or more images on an image-by-image basis; in response to the mobile terminal device being brought within the communicable distance from the printer while the first screen on which the selected image data set is identified is being displayed on the display unit before the preview button is operated, output a first print instruction to print the respective multiple images corresponding to all of the one or more pieces of image data contained in the selected image data set; in response to the mobile terminal device being brought within the communicable distance from the printer while the preview screen on which the intended image of the selected image data set is identified is being displayed on the display unit after the preview button is operated, output a second print instruction to print the intended image identified on the preview screen; control the display unit to display the first screen without displaying the preview screen; and control the display unit to display the preview screen without displaying the first screen. a display unit; a near field wireless communication unit configured to perform near field wireless communication with a printer within a communicable distance from the printer; and a controller configured to: control the display unit to display a first screen configured to show one or more image data sets each containing one or more pieces of image data and accept a selection of a data set with multiple images from the one or more image data sets; control the display unit to display a preview button wherein, in response to a tapping operation of the preview button, the display unit displays, on a preview screen, one or more images corresponding to the one or more pieces of image data contained in the selected image data set by displaying an intended image of the one or more images on an image-by-image basis; in response to the mobile terminal device being brought within the communicable distance from the printer while the first screen on which the selected image data set is identified is being displayed on the display unit before the preview button is operated, output a first print instruction to print the respective multiple images corresponding to all of the one or more pieces of image data contained in the selected image data set; in response to the mobile terminal device being brought within the communicable distance from the printer while the preview screen on which the intended image of the selected image data set is identified is being displayed on the display unit after the preview button is operated, output a second print instruction to print the intended image identified on the preview screen; control the display unit to display a first screen configured to show one or more image data sets each containing one or more pieces of image data and accept a selection of a data set with multiple images from the one or more image data sets; control the display unit to display a preview button wherein, in response to a tapping operation of the preview button, the display unit displays, on a preview screen, one or more images corresponding to the one or more pieces of image data contained in the selected image data set by displaying an intended image of the one or more images on an image-by-image basis; in response to the mobile terminal device being brought within the communicable distance from the printer while the first screen on which the selected image data set is identified is being displayed on the display unit before the preview button is operated, output a first print instruction to print the respective multiple images corresponding to all of the one or more pieces of image data contained in the selected image data set; in response to the mobile terminal device being brought within the communicable distance from the printer while the preview screen on which the intended image of the selected image data set is identified is being displayed on the display unit after the preview button is operated, output a second print instruction to print the intended image identified on the preview screen; control the display unit to display the first screen without displaying the preview screen; and control the display unit to display the preview screen without displaying the first screen.