This research aims were 1) study factors affecting internal control of the Power Development Fund 2) assess the effectiveness of the internal control of the Power Development Fund and 3) test the relationship between factors affecting the effectiveness of the internal control of the Power Development Fund. Based on 175 internal and external staffs working with the organization, the data were collected by questionnaire and analyzed with frequency, percentage, mean, standard deviation. In addition, the relationship between factors affecting the internal control of the Power Development Fund was studied. The
correlation of the measured variables by correlation analysis method was examined, including plural regression analysis. The results of the study showed that 1) Factors affecting the internal control of the Power Development Fund were at a high level, namely factors on organizational structure, compliance factors, executive factors, information and communication factors, whereas personnel development factors were at moderate level. 2) The effectiveness of the internal control of the Power Development Fund was at a high level in all components. 3) Factors having a positive effect on the effectiveness of internal control of the Power Development comprise factors on organizational structure, compliance factors, management factors, information and communication factors. For personnel development factors, there isno relationship to the effectiveness of the internal control of the Power Development Fund.