To change software without losing data before change in changing the software held as master data.

When a change content accepting means 21 accepts change content with respect to master data 34, a pre-change data storage means 31 is made to store change data in the previous change time stored in a change data storage means 32, and the change data storage means 32 is made to store the change content accepted this time. A change content comparing means 22 reads this time change data stored in the change data storage means 32 and the pre-change data stored in the pre-change data storage means 31 for several times, and visually displays the comparison content, and extracts only the section changed this time as change difference data. This extracted change difference data stored in a change difference data storage means 33 are connected to master data 34 by a difference data connecting means 23.