A printer that performs printing on a printable medium to be attached to a product, comprising a top cover and a main cover; a handy scanner that reads identification information uniquely identifying the product on which the medium is to be attached; a memory that records a product information file that records, for each piece of the identification information, product information including a plurality of pieces of data of a plurality of attribution items each representing an attribution of the product, wherein the memory is configured to record print data in association with the identification information printed in the past by the printer, the plurality of pieces of data of the plurality of attribution items being arranged at predetermined positions in the print data; a printer mechanism provided in the main cover that prints the product information of the product identified by the read identification information, on the printable medium on the basis of the print data; a display provided on the top cover that displays a print image of the printable medium where the product information is to be printed by the printer mechanism; a controller that reads, where the identification information is read by the handy scanner, the product information from the product information file in the memory on the basis of the identification information, generates print data in which the plurality of pieces of data included in the read product information are arranged at predetermined positions, detects an attribution item that differs between the generated print data and the print data that is recorded in the memory in association with the read identification information, and displays the print image on the display on the basis of the generated print data in such a way that the detected attribution item is highlighted. a top cover and a main cover; a handy scanner that reads identification information uniquely identifying the product on which the medium is to be attached; a memory that records a product information file that records, for each piece of the identification information, product information including a plurality of pieces of data of a plurality of attribution items each representing an attribution of the product, wherein the memory is configured to record print data in association with the identification information printed in the past by the printer, the plurality of pieces of data of the plurality of attribution items being arranged at predetermined positions in the print data; a printer mechanism provided in the main cover that prints the product information of the product identified by the read identification information, on the printable medium on the basis of the print data; a display provided on the top cover that displays a print image of the printable medium where the product information is to be printed by the printer mechanism; a controller that reads, where the identification information is read by the handy scanner, the product information from the product information file in the memory on the basis of the identification information, generates print data in which the plurality of pieces of data included in the read product information are arranged at predetermined positions, detects an attribution item that differs between the generated print data and the print data that is recorded in the memory in association with the read identification information, and displays the print image on the display on the basis of the generated print data in such a way that the detected attribution item is highlighted. reads, where the identification information is read by the handy scanner, the product information from the product information file in the memory on the basis of the identification information, generates print data in which the plurality of pieces of data included in the read product information are arranged at predetermined positions, detects an attribution item that differs between the generated print data and the print data that is recorded in the memory in association with the read identification information, and displays the print image on the display on the basis of the generated print data in such a way that the detected attribution item is highlighted.