A monitoring device includes: a communication interface configured to receive image data acquired by a camera and a signal generated by at least one sensor; a screen configured to display thereon the received image data as a main image; and a controller configured to control operations of the communication interface and the screen, wherein the controller controls the screen to include a control area around an area for displaying the main image so that the control area displays the main image and a surrounding image of the main image, and wherein, in response to the sensor sensing at least one event, the controller controls generation of an alarm with indication of at least one pointer associated with the sensor in the control area as a source of the sensing the event, and controls the main image to be changed to cover an area where the sensor is disposed.