A design assistance system (S) for designing an item with reference to a model of the item, the design assistance system comprising: an item recognition unit that recognizes the item to be designed; a designation condition recognition unit that recognizes designation conditions that are manufacturing conditions designated for each of a plurality of sections included in the item; an error condition recognition unit that recognizes an error condition that is one of the designation conditions corresponding to at least one of a section where an error occurs in manufacturing the item and a section where the error may occur, based on the designation conditions and predefined error criteria; an elimination condition recognition unit that recognizes an elimination condition that is one of the designation conditions for eliminating the error by making a change based on the error condition and a predefined error elimination standard; and a display content determination unit that controls a display unit to display the model of the item, characterized in that the display content determination unit controls the display unit to: highlight an error section that is the section corresponding to the error condition and display at least one of the elimination condition and an elimination section that is a section corresponding to the elimination condition; and display the model of the item in a manner that each section can be selected and display at least one of the elimination condition and the elimination section when the error section is selected. an item recognition unit that recognizes the item to be designed; a designation condition recognition unit that recognizes designation conditions that are manufacturing conditions designated for each of a plurality of sections included in the item; an error condition recognition unit that recognizes an error condition that is one of the designation conditions corresponding to at least one of a section where an error occurs in manufacturing the item and a section where the error may occur, based on the designation conditions and predefined error criteria; an elimination condition recognition unit that recognizes an elimination condition that is one of the designation conditions for eliminating the error by making a change based on the error condition and a predefined error elimination standard; and a display content determination unit that controls a display unit to display the model of the item, characterized in that the display content determination unit controls the display unit to: highlight an error section that is the section corresponding to the error condition and display at least one of the elimination condition and an elimination section that is a section corresponding to the elimination condition; and display the model of the item in a manner that each section can be selected and display at least one of the elimination condition and the elimination section when the error section is selected. highlight an error section that is the section corresponding to the error condition and display at least one of the elimination condition and an elimination section that is a section corresponding to the elimination condition; and display the model of the item in a manner that each section can be selected and display at least one of the elimination condition and the elimination section when the error section is selected. <EOS>