The term '"digital divide" refers to the gap between individuals, households, businesses and geographic areas at different socio-economic levels with regard both to their opportunities to access information and communication technologies and to their use of the internet for a wide variety of activities. The article mainly discusses the problem of digital divide and public libraries' missions. Firstly, it explains what digital divide is and how to make measurement. Secondly, it explores what the missions are and roles of modern public libraries in the networked world. Thirdly, it reports some projects of bridging digital divide, which were undertaken in the United States, Great Britain and all of the world. Finally, it makes some conclusions and suggestions to public libraries in Taiwan to bridge digital divide.