A program processing apparatus processes an HMI program for factory automation. The program processing apparatus includes a control unit that controls the program processing apparatus. The control unit includes a detection unit that detects, based on at least a data type and a data size, identical sets of user interface data from a data group including a plurality of sets of user interface data corresponding to UI functions of the HMI program, and a change unit that changes the data group to include only one of the identical sets of user interface data.