The term, museum, was used to describe different things as time changes. In the classical period the museum meant “a place of contemplation or a shrine of the Muses” and the Romans described the place designated for discussing philosophical matters as a museum. From the fifteenth century through seventeenth century, a museum was related to its collections of curiosities, and by the eighteenth century museum meant an institution which collects, preserves, and displays its collection, and opens its door to the public. From the late eighteenth century the museum was more related to its building. Its temple-like building gave the museum distinguished characteristics of the museum from the ordinary place. Museums were built in the manner of giving the atmosphere of the sacred place. But in modern times museum is more related to its collection and gets its unique nature by its collection.(Woodhead and Stansfield 1989, 3) How the American Association of Museums has changed the museum ethics by saying that the museum does not have to have collections. That means that probably in the future museums will be more related to their activities. The activities of museums can be divided basically into three categories: acquisition; preservation and conservation; exhibition and interpretation. Among these basic activities, exhibition and interpretation are the educational roles of museum, and the other categories of activities - acquisition, preservation and conservation - are ultimately for the educational purpose of museums. So the main purpose of museums is the education of their public. Not only is the museum supported by the public. It's future lies in this support. Support increases when interest increases. Therefore expanding and exploring educational functions of the museum are crucial. This point is made clearer in relation to the characteristics of collections. Collections exist for the public, using objects that the public used. And in most cases, museums are located in an ideal setting within the local community. This emphasizes the cultural and educational aspect of the museum in terms of social service to the community. This paper explains the unique quality of museum education and various methods of fulfilling the mission of the museum education. This paper concludes with the notion that for the 21st century more emphasis should be put on museum's educational mission and its development.