Recently the demand to make software resistant to manipulation is increasing. Similarly the demand to hide operation of software or to hide secret used in software is increasing. Software possessing such properties is called tamper-resistant software. One of methods to realize tamper-resistant software is obfuscation of software, and evaluating such software objectively and quantitatively has been an important research subject. One of the known objective and quantitative methods is the method using a parse tree of a compiler proposed in [GMMS00]. This method takes into account the complexity in one module of software but not the complexity originated from relationships among modules. We propose at first several obfuscation methods to create a complicated module structure which violates the structured programming rules. Then, we propose a new evaluation method which can measure the difficulty caused by complicated structure among modules. Its effectiveness is proven through experiments. One of experiments shows the grades obtained by the proposed evaluation well reflects the actual reading time required by analysts.