The purposes of this study were 1) to study the level of professional learning community of schools and the level of factors affecting the professional learning community of schools 2) to find out the relationship between the factors affecting the professional learning community and the professional learning community of schools 3) to determine the factors affected the professional learning community 4) to construct the predictive equation of the professional learning community of schools. The samples of this study were 400 teachers drawn from schools under Loei Primary Educational Service Area Office 2 which by the stratified random sampling method. A rating scale questionnaire was applied for data gathering and statistics used for data analysis were frequency, percentage, mean, standard deviation, Pearson's product moment correlation coefficient and multiple regression. The study findings revealed as follows : 1) the level of professional learning community of schools and the level of all factors was found clearly in overall aspect at the high level 2) the factors were positive correlated with the professional learning community of schools with the statistical significance at .01 level 3) the factors of collective teacher efficacy (X3), transformational leadership (X1) and school climate (X2) affected the professional learning community of schools with the statistical significance at .01 level and the efficiency in prediction was 78.30 percent (R2=.783). The predictive equation as follows : The predictive equation in raw scores : Y ̂=.504+.367X_3+.300X_1+.211X_2 The predictive equation in standard scores : Z ̂=.366Z_(X_3 )+.357Z_(X_1 )+.235Z_(X_2 )