This study aimed at clarifying the “personal teaching theory (PTT)” of teachers as to how to give lessons in mathematics. PTT is supposed to be a belief system involved in everyone's teaching activity. The subjects were 592 elementary and 286 junior high school teachers. They were asked to respond to a questionaire with a 6-point bipolar scale, describing actual teaching activities on mathematics. Factor analysis of their responses yielded six factors: Teaching paces (student-centered vs. teacher-centered), Teaching styles (heuristic vs. explanation), Use of materials (textbook-centered vs. flexible use), Homework (required vs. not required), Teaching processes (rigid vs. flexible), Planning lessons (consulting with colleagues vs. self deciding). The PTT profiles of lessons were derived in terms of these six factors; also the profiles were derived toward the students good at mathematics as well as those doing poorly at it.