An optical disk player comprising: an optical pickup for reading out signals from an optical disc by irradiating a laser beam on the optical disk; a signal processor for processing the signals read out by the optical pickup; a decoder for decoding the signals processed by the signal processor; an HDMI (High-Definition Multimedia Interface) output terminal to which a monitor display device is connectable through an HDMI cable and for outputting the signals decoded by the decoder to the monitor display device through the HDMI cable; a main controller for controlling the optical pickup, the signal processor, and the decoder; and a remote controller operable by a user to input various commands to the main controller, wherein the main controller is adapted to obtain information relating to resolutions that the monitor display device supports; when a high-resolution video is not appropriate to the user, and when a command for switching the resolution of the monitor display device is inputted first through the remote controller by the user, the main controller converts video signals among the signals decoded by the decoder to have a resolution of lowest level among the resolutions that the monitor display device supports and outputs the converted video signals to the monitor display device to change the resolution of the monitor display; characterized in that when the command is inputted additionally, the main controller switches the resolution of the video signals sequentially to increase the resolution degree by one level among the resolutions that the monitor display device supports whenever the command is inputted, when the command is inputted while the monitor display device displays images at highest resolution, the main controller stops to output the video signals to the monitor display device, and when the specific key corresponding to the command for switching the resolution of the monitor display device is pressed down additionally while the output of the video signals is stopped, the video signals having the resolution of the lowest level is started to be outputted to the monitor display device again. an optical pickup for reading out signals from an optical disc by irradiating a laser beam on the optical disk; a signal processor for processing the signals read out by the optical pickup; a decoder for decoding the signals processed by the signal processor; an HDMI (High-Definition Multimedia Interface) output terminal to which a monitor display device is connectable through an HDMI cable and for outputting the signals decoded by the decoder to the monitor display device through the HDMI cable; a main controller for controlling the optical pickup, the signal processor, and the decoder; and a remote controller operable by a user to input various commands to the main controller, wherein the main controller is adapted to obtain information relating to resolutions that the monitor display device supports; when a high-resolution video is not appropriate to the user, and when a command for switching the resolution of the monitor display device is inputted first through the remote controller by the user, the main controller converts video signals among the signals decoded by the decoder to have a resolution of lowest level among the resolutions that the monitor display device supports and outputs the converted video signals to the monitor display device to change the resolution of the monitor display; characterized in that when the command is inputted additionally, the main controller switches the resolution of the video signals sequentially to increase the resolution degree by one level among the resolutions that the monitor display device supports whenever the command is inputted, when the command is inputted while the monitor display device displays images at highest resolution, the main controller stops to output the video signals to the monitor display device, and when the specific key corresponding to the command for switching the resolution of the monitor display device is pressed down additionally while the output of the video signals is stopped, the video signals having the resolution of the lowest level is started to be outputted to the monitor display device again.