Software architecture is a core asset for any organization that develops software-intensive systems. The purpose of the architecture evaluation of a software system is to analyze the architecture to verify that the quality requirements have been addressed in the design. An organization can design the best architecture for their system using an architecture evaluation method. Unsuitable architecture can precipitate disaster because the architecture determines the structure of the project. To prevent this issue, we have to evaluate software architecture. However, current evaluation methods focus on single product architecture, not product line architectures and hardly considered the characteristics of product lines, such as variation points. We need to create new evaluation method, or extend current architecture evaluation methods to evaluate software product line architectures. This article will focus on the latter, identifying the problem and specific characteristic of evaluating product line architectures. This article introduces the idea of extending the Architecture Trade-off Analysis method (ATAM) to assessing product line architecture. This method has been validated through a case study, involving microwave oven software in the appliance domain by extending ATAM. Product line architecture must identify and accommodate the variation points among its family members. Extended ATAM can do this, but ATAM cannot. Product line architecture has a lot of variant as variation points. It is difficult to create a utility tree with all variation points of product line architecture. Extended ATAM handles this issue by using extended PLUC tags because the numerous the variation points of product line architecture can be expressed more simply and can be added or changed more easily by using tags. The goal of my approach is to analyze the characteristics of product line architecture and then to apply their variation points to architecture evaluation methods. Among the many...