English teachers, especially those who teach summary writing to students with relatively lower proficiency in English face difficulty in teaching summary writing and while assessing their students' performances. In the classroom context, an analytic rubric is pedagogically more helpful than a holistic rubric because the teacher can confirm the strengths and weaknesses of their students' summary performance and the students can receive constructive feedback (Yamanishi et al., 2019). This study examined the practicality of the analytic rubric which consisted of four rating scales, including language use, by investigating seven in-service English teachers' honest assessment of 160 summaries of Japanese private university students who are inexperienced in writing English summaries and have lower-intermediate proficiency of English. Furthermore, this study examined the dependability of the analytic rubric using multivariate generalizability theory (Brennan, 2001). The results showed that assessing language use and judging summaries, copied, to a lesser or greater extent, from the source text was difficult because of diverse linguistic errors and the use of paraphrasing was lacking. Therefore, it is necessary to define the gravity of language errors and that of copying in more detail to develop a rubric that suits to assess the summaries written by English learners with lower-intermediate level of English.