Professional communication skills in writing and speaking with multiple and complex audiences are required to engineers in society of modern technology. In this paper, we proposed the effective assessment system for the Program Outcomes on the communication skill competence(PO7), which is one of the 12 program outcomes stipulated by ABEEK (Accreditation Board for Engineering Education of Korea). To ensure logical connectivity of the assessment system, we carefully selected the performance criteria by defining the core concept of "written communication" and "verbal communication". Based on the selected performance criteria, the whole process of creating assessment tools and rubrics was explained in detail. It can be expected that the assessment for the Program Outcomes on the communication skill competence would be more systematic by using the proposed assessment system.