An antitheft system of a user terminal module and a mobile robot capable of being used as a shopping cart are disclosed. The antitheft system includes: a user terminal module generating terminal location data comprising location coordinates; a mobile robot assisting in driving through conversion of a drive mode into a preset drive mode depending upon a location of the user terminal module and a distance from the mobile robot to the user terminal module while generating and outputting robot location data comprising location data thereof in real time; and a monitoring device monitoring locations of the user terminal module and the mobile robot in real time and controlling the terminal module and the mobile robot to perform an antitheft operation depending upon a region in which the terminal module and the mobile robot are placed, thereby improving reliability by preventing theft and loss of the user terminal module and the mobile robot.