An intercom system comprising: a plurality of entrance slave units (305, 305-1,..., 305-n) each of which is attached to each residence and comprises an operation unit and a camera; a plurality of living room master units (302, 302-1,..., 302-n) each of which is configured to perform communication with the corresponding entrance slave unit; a control unit capable of performing communication with the plurality of living room master units; characterized by comprising an external device (303-1 to 303-n) having a display unit for displaying information on a guide route from a departure place to a destination, the information on the guide route being set based on user input information, and configured to perform communication with the control unit and to transmit a request signal comprising the user input information to the control unit, wherein the control unit is configured to acquire identification information of each of the plurality of entrance slave units and image data captured by the camera via each of the plurality of living room master units, to generate suspicious person information about a suspicious person, based on the identification information and the image data, and to transmit, to the external device, the suspicious person information associated with the external device among the generated suspicious person information, based on the user input information included in the request signal from the external device, wherein the suspicious person information associated with the external device is the suspicious person information generated based on the identification information and the image data acquired from an entrance slave unit existing in a predetermined region comprising the guide route, and wherein the external device is configured to display, on the display unit and further to the information of the guide route set based on the user input information, the suspicious person information, and map information. a plurality of entrance slave units (305, 305-1,..., 305-n) each of which is attached to each residence and comprises an operation unit and a camera; a plurality of living room master units (302, 302-1,..., 302-n) each of which is configured to perform communication with the corresponding entrance slave unit; a control unit capable of performing communication with the plurality of living room master units; characterized by comprising an external device (303-1 to 303-n) having a display unit for displaying information on a guide route from a departure place to a destination, the information on the guide route being set based on user input information, and configured to perform communication with the control unit and to transmit a request signal comprising the user input information to the control unit, wherein the control unit is configured to acquire identification information of each of the plurality of entrance slave units and image data captured by the camera via each of the plurality of living room master units, to generate suspicious person information about a suspicious person, based on the identification information and the image data, and to transmit, to the external device, the suspicious person information associated with the external device among the generated suspicious person information, based on the user input information included in the request signal from the external device, wherein the suspicious person information associated with the external device is the suspicious person information generated based on the identification information and the image data acquired from an entrance slave unit existing in a predetermined region comprising the guide route, and wherein the external device is configured to display, on the display unit and further to the information of the guide route set based on the user input information, the suspicious person information, and map information.