An image-forming system comprising: an image-forming device including: a printing engine part for carrying out printing and a portable terminal including: an image-capturing part, a storage part for storing an application, and a display part for displaying an image and a screen, characterized in that the image-forming device further includes: a state-detecting part for detecting a state of the image-forming device, and a panel part that includes a plurality of light-emitting elements for displaying the state of the image-forming device, the panel part adapted such that, while the state of the image-forming device is being displayed to a user by the light-emitting elements, a turned-on/turned-off pattern of the plurality of light-emitting elements is switched, and optical signals destined for the portable terminal and including information on the state of the image-forming device are transmitted, the portable terminal further includes: a processing part configured to identify, based on the application launched, the information on the state of the image-forming device included in the optical signals from image data obtained as a result of the image-capturing part capturing an image of the panel part, and to display, based on the application, the state of the image-forming device on the display part; wherein: one of the light-emitting elements among the plurality of light-emitting elements is a reference light-emitting element for relaying to the portable terminal that the optical signals are being transmitted, the panel part is configured to transmit the optical signals by using the light-emitting elements to the portable terminal in a communication display interval provided between normal display intervals, wherein the communication display interval is an interval during which communication display to the user is carried out; the reference light-emitting element, when maintained in an on state in a normal display interval for state display for the user, is configured to be temporarily turned off in a communication display interval between normal display intervals(tl), the reference light-emitting element, when maintained in an off state in a normal display interval, is configured to be temporarily turned on in the communication display interval, to enable the portable terminal to identify whether or not the optical signals are being transmitted, the panel part is configured to communicate information by switching the turned-on/turned-off pattern of the light-emitting elements other than the reference light-emitting element in the communication display interval, and the processing part is configured to identify state information contained in the optical signals from image data obtained by image capture by the image-capturing part while the optical signals are being transmitted with the reference light-emitting element in the on or off state. an image-capturing part, a storage part for storing an application, and a display part for displaying an image and a screen, a state-detecting part for detecting a state of the image-forming device, and a panel part that includes a plurality of light-emitting elements for displaying the state of the image-forming device, the panel part adapted such that, while the state of the image-forming device is being displayed to a user by the light-emitting elements, a turned-on/turned-off pattern of the plurality of light-emitting elements is switched, and optical signals destined for the portable terminal and including information on the state of the image-forming device are transmitted, one of the light-emitting elements among the plurality of light-emitting elements is a reference light-emitting element for relaying to the portable terminal that the optical signals are being transmitted, the panel part is configured to transmit the optical signals by using the light-emitting elements to the portable terminal in a communication display interval provided between normal display intervals, wherein the communication display interval is an interval during which communication display to the user is carried out; the reference light-emitting element, when maintained in an on state in a normal display interval for state display for the user, is configured to be temporarily turned off in a communication display interval between normal display intervals(tl), the reference light-emitting element, when maintained in an off state in a normal display interval, is configured to be temporarily turned on in the communication display interval, to enable the portable terminal to identify whether or not the optical signals are being transmitted, the panel part is configured to communicate information by switching the turned-on/turned-off pattern of the light-emitting elements other than the reference light-emitting element in the communication display interval, and the processing part is configured to identify state information contained in the optical signals from image data obtained by image capture by the image-capturing part while the optical signals are being transmitted with the reference light-emitting element in the on or off state.