The objectives of this research were: 1) to study the changes according to Mathematics Teachers Standard of teachers obtaining development by using Lesson Study, and 2) to study the learning achievement of students taught by Mathematics Teachers obtaining development by using lesson study. The target group included mathematics teachers, and pratomsuksa 3 students of Huaimekratnukul School, under jurisdiction of Kalasin Primary Educational Service Area Office 2, Kalasin Province, in 2016 school year. The design was mixed methods. The instrument using in this study included: 1) the assessment form of mathematics teacher, 2) the learning achievement test, 3) the observation record orm, 4) the teacher standard evaluation form, 5) the interview form. Data were analyzed by content analysis, percentage, mean and standard deviation. The research findings found that: 1) For mathematics teacher standard evaluation of teachers obtaining development by using lesson study, every one was at “Very Good” level. Their evaluation scores were between 85.27 – 90.43 Their percentage average scores 87.52 which was at “Very Good.” The evaluative findings were at “Very Good” level. 2) For mathematics teacher professional standard the learning achievement of students taught by teachers developing by using lesson study, they had development and change in confidence, assertion, good attitude towards mathematics learning, mathematics process skill, and social skill at a higher level.