In rural development process, demographic indexes are of most important ones. Fertility is one of the most important factors affecting population growth. Determining the factors affecting fertility in rural areas, is important in population planning. The aim of this research is to recognize socio-economic and demographic factors affecting fertility in rural areas of Najaf-Abad township. The analyzed sample includes 415 married rural women who were 10 to 49 years old at the research time, and were in first marriage status with at least one alive child. Data obtained from existing information in rural women’s household folders in Najaf-Abad health houses. For analysis, software was used. Pearson Correlation Coefficients for pairs of variables were used. Multi variate regression analyses were also carried out. Results showed that variables of woman age group of 40-44 years, husband age group of 46-55 years, woman marriage with 20 years and older, marriage period length, number of child mortality, number of abortion and village total area of useful land (proxy for the size of the village), have positive and statistically significant effect on fertility. Variables of woman age, woman age at first partum, mean of birth interval, woman reading and writing and elementary education levels, husband reading and writing education level, husband being employed, husband being employed in service and selling jobs and having insurance, have negative and statistically significant effect on fertility. It is suggested that in population policy makings, expansion of the level of education and upgrading the health level for the purpose of decreasing child mortality and abortion, be considered. Also, right time of the first partum and proper birth intervals, should be taught to mothers by appropriate trainings. Furthermore, larger number of families should be covered by insurance advantages. Since high level of education of the couple and husband being employed will decrease the number of children, lower fertility rate can be considered as one of the objectives of improvement in higher levels of education and employment.