Since its first appearance in the late 1950s, Neoclassical economic theory of fertility, especially as exemplified by Gary Becker's model of household production function that assumed a unitary utility function of the household, has become one of the most popular paradigms to examine fertility changes. This paper intends to expand the economic model by incorporating the social network approach into the original paradigm. Social networks are crucial in determining the fertility rate of a society above and beyond parameters originally included in the neoclassical economic model in two ways. First, the extent that separate utilities of spouses could be treated in one function is, in part, dependent on the network embeddedness of spouses: intra-household network. If spouses are not embedded into each other's networks, it would be natural to drop the assumption of the unitary utility function and reformulate the decision process based on bargaining. Second, in addition to the intra-household network, inter-house networks also play a role in couple's decisions with regard to fertility. Couples need information about other couples' fertility decisions for their own and also normative pressures from other couples or friends are crucial in the dynamic process of fertility change. Social networks are a major conduit both for information and normative constraints. This paper focuses on the first kind of networks (intra-household networks) with illustrative empirical results by using the two waves of Korean Longitudinal Survey of Women and Families (KLOWF).