Software Product Line Engineering is an approach to efficient maintenance of a software product family.
Software products which has applied this approach are called Software Product Line. 
Re-engineering existing software product into software product lines is important task. 
However, analyzing all software in the software family is hard task so the criteria for selecting initial products for construction of software product lines is needed. 
Relationships about how software was evolved and when branched is useful information, but it is occasionally not available.
In this research, we construct a Software Derivation Tree that approximates the derivation of software products.
Our approach takes only source code of software family as an input.
A software derivation tree is defined as a minimum spanning tree whose cost function is based on the number of similar source files.
We conducted a case study with open source software projects.
The result shows that about 86% of edges in software derivation trees are consistent with the actual version history.