This paper provides the analysis of economic theories about bundling in telecommunications service. First, the negative aspect of bundling is discussed. Second, the competitively neutral aspect of bundling which is counter response of negative effect is analyzed. Third, some variables affecting the bundling is investigated and the corresponding effect of bundling is discussed. The bundling can increase the social welfare under some circumstance while it sometimes decreases economic efficiency by detering the entry of competitive firms. Finally, regulatory approaches on bundling such as the criteria of bundling provision, the requirement of equal access, the discounting scheme ad a price control, ex anti regulation vs. ex post regulation, and the criteria of predatory pricing are provided.