This research aimed to study: 1) the internal supervision process under Saraburi Primary Educational Service Area Office 2, 2) the teachers teaching behaviors under Saraburi Primary Educational Service Area Office 2, and 3) the relationship between the internal supervision process and teachers teaching behaviors under Saraburi Primary Educational Service Area Office 2. The samples of this research were 310 teachers under Saraburi Primary Educational Service Area Office 2. The research instruments were 5 rating scale questionnaires with reliability of 0.94 and 0.90. The statistics used for data analysis were to obtain various descriptive statistics such as frequency, percentage, mean, standard deviation, Conbach's alpha coefficient and Pearson's correlation coefficient. The finding were as follows: 1. The internal supervision process under Saraburi Primary Educational Service Area Office 2 in educational institution was at the high level. When considering each aspect in every level with average values in descending order, as follows: Media creation and tools, Supervision planning, Supervisory practice and Education current conditions problems and needs. 2. The teacher's teaching behavior under Saraburi Primary Educational Service Area Office 2 as a whole was at the high level. When considering each aspect in every level with average values in descending order as follows: learning activities, the use of media and technology, supervisory practice and classroom research. 3. The internal supervision process and teacher's teaching behavior under Saraburi Primary Educational Service Area Office 2. Had a high level of positive relationship with the correlation coefficient between 0.71 and 0.89, which has a significant positive correlation at level 0.1. The results of the research concluded that internal supervision process affects teachers' teaching behavior at a high level. Therefore there must pay attention to the supervision process within the educational institution by having a systematic operation plan in accordance with the internal supervision system. So that teachers have appropriate teaching behavior, appropriate teaching behavior, leading to self-development and develop learners to high quality.