Service importance has been growing increasingly as competition element of enterprises according to going on rapid softness, information and knowledge of industrial infrastructure recently. Quality management system that implemented in manufacturing sector have been spreading rapidly to service company, but the company performing pure engineering service only in construction fields performed mainly the evaluation on the operational aspect such as degree of implementation of the established system because it is difficult to objective evaluation on the activity of the established quality management system or quality assurance system. This study would like to make on offer the improvement points based on the evaluation of service quality and the itself evaluation result through the questionnaire on the service offerers and customers using the pre-qualified SERVQUAL model in establishment of the improvement goal of the company. According to the result of this study, it is analyzed a gap and required to establish a counter-plan to correct many gaps discovered between the real offered level and the expect level of custom.