The study was aimed at describing: the quality of lesson study; the quality of student learning activities; and the improvement of students achievement before and after lesson study. The subject of study was 4 lecturers majoring in physics education and one class of students of Physics Education Department, Ganesha University of Education. The object of research was quality lesson study, learning activities, and students’ achievement at basic physics-6. The type of research was case study with qualitative description analysis. The quality of lesson study was measured by observation of plan, do, and see. The improvement of learning activity was measured by observation and interview, and students’ achievement quality in basic physics-6 was measure by test. The results showed: the quality of lesson study is good category; the student learning activity during the lesson study as active category; and the students’ achievement at basic physics-6 after lesson study improved with good category (before lesson study : x ¯ 1 = 41.2 bad category and after lesson study: x ¯ 2 = 73.8 good category)