Subcategory of expertise required of teachers is very diverse. This paper focused on expertise associated with the assessment ability of teachers among them. The assessment expertise of teachers is divided into ‘capability to be able to assess learner’s performance or the level and quality of knowledge’ and ‘capability to deliver such assessment results properly to learners’. This paper is trying to collect basic data for educating the assessment speech of teachers and to analyze how the aspect of teacher’s assessment speech varies depending on the teacher’s life cycle. Accordingly, 21 pre-service teachers and 6 experienced teachers at the mature stage teaching Korean for 5 to 15 years were targeted, and their assessment speech data were collected and analyzed. As a result, pre-service teachers had a predominant tendency to obtain a quantitative balance when presenting students with ‘positive content’ and ‘negative content’. In addition, the pre-service teachers had a lower proportion in ‘presenting alternatives’ after indicating problems shown in learner’s speech, and responded that ‘they didn’t have any idea to be able to solve problems the learners had shown’. In connection with this, experienced teachers also told that ‘they were not so sure about the specific alternative to be able to solve the problems of learner’s speech’. Finally, in the assessment speech of pre-service teachers hardly, the attempt to ‘try to present assessment result through interaction with learners’ hardly appeared. The result of this study is presenting the current aspect of ‘teachers’ assessment speech’ pre-service teachers and experienced teachers, and implying that the education on ‘teachers’ assessment speech’ to meet their needs to both pre-service and experienced teacher is required.