A digital loss/accident defense system for preventing an act by a suspicious person by monitoring a video shot by a monitoring camera installed so as to cover a surveillance target area being a staff-only area where unauthorized entry is prohibited, comprising: a monitoring device including: positional information acquiring means for acquiring positional information of mobile terminal devices being carried by a plurality of employees respectively throughout the surveillance target area; face image storing means for accumulating a face image of an authenticated person; face authentication collating means for collating a face image of a person shot by the monitoring camera with the face image accumulated in the face image storing means; and control means for, if a result of collation by the face authentication collating means is a non-match with an authenticated person's face image, determining him/her as a suspicious person, determining a position of the mobile terminal device closest to the suspicious person based on the positional information acquired from the positional information acquiring means, and transmitting information regarding the suspicious person to said mobile terminal device; and said mobile terminal device including a response-inability setting unit that presets not being able to answer back to information transmitted from said monitoring device and returning, when response-inability has been set by said response-inability setting unit, an answer-back of said response-inability if transmission of information is received from said monitoring device, wherein the control means is characterized by, if an answer-back of response-inability is returned from the mobile terminal device, determining a position of the mobile terminal device the second closest to the suspicious person, and transmitting the information regarding the suspicious person to said second closest mobile terminal device, and the information regarding the suspicious person includes information of a position of the suspicious person and a position of the mobile terminal device to which the information has been transmitted overlapped on the surveillance target area. a monitoring device including: positional information acquiring means for acquiring positional information of mobile terminal devices being carried by a plurality of employees respectively throughout the surveillance target area; face image storing means for accumulating a face image of an authenticated person; face authentication collating means for collating a face image of a person shot by the monitoring camera with the face image accumulated in the face image storing means; and control means for, if a result of collation by the face authentication collating means is a non-match with an authenticated person's face image, determining him/her as a suspicious person, determining a position of the mobile terminal device closest to the suspicious person based on the positional information acquired from the positional information acquiring means, and transmitting information regarding the suspicious person to said mobile terminal device; and positional information acquiring means for acquiring positional information of mobile terminal devices being carried by a plurality of employees respectively throughout the surveillance target area; face image storing means for accumulating a face image of an authenticated person; face authentication collating means for collating a face image of a person shot by the monitoring camera with the face image accumulated in the face image storing means; and control means for, if a result of collation by the face authentication collating means is a non-match with an authenticated person's face image, determining him/her as a suspicious person, determining a position of the mobile terminal device closest to the suspicious person based on the positional information acquired from the positional information acquiring means, and transmitting information regarding the suspicious person to said mobile terminal device; and said mobile terminal device including a response-inability setting unit that presets not being able to answer back to information transmitted from said monitoring device and returning, when response-inability has been set by said response-inability setting unit, an answer-back of said response-inability if transmission of information is received from said monitoring device, wherein the control means is characterized by, if an answer-back of response-inability is returned from the mobile terminal device, determining a position of the mobile terminal device the second closest to the suspicious person, and transmitting the information regarding the suspicious person to said second closest mobile terminal device, and the information regarding the suspicious person includes information of a position of the suspicious person and a position of the mobile terminal device to which the information has been transmitted overlapped on the surveillance target area.