This paper compares peace museums and military museums in Japan and foreign countries. It analyses the features, social functions of both peace and military museums, and considers the social influence on both museums. A public relations facility of the Self Defense Forces is regarded as a military museum in Japan, so the development and contents of the exhibition of such public relations facilities are analyzed. A half of them were established in a period between 1964 and 1969. Three new large public relations facilities by each SDF were established and they gather a lot of visitors. The contents of the exhibition are shifting from a type succeeding former army to a type explaining the SDF. The ways to exhibit wars are different between peace museums and military museums. A social function of peace museums in Japan and other countries is to succeed the last war experience to the next generation. They let visitors determine not to repeat a disastrous war and have the will for a peaceful world. As a potential function, visitors are led to pacifism opposing any war and distrust to patriotism that causes war. On the other hand, a social function of military museums is to succeed the defense war and the liberation war. They let visitors to consider national defense and enlighten their patriotism. War memorials and national graveyards commemorate those who died on duty in wars for their motherland. Compared with peace museums, military museums in the world have a bigger number of their establishment, a longer history, and larger in scale. The social influence of military museums in the world is bigger than that of peace museums.