Nowadays, beach erosions have spread to most all over sand beaches in Japan. These causes are as follows,
1) Many undertakings for rivers and beaches (Ex. constructions of dams) have been made. Therefore, supply of sand has deccreased.
2) Scopes of human activities have spread to coasts and a lot of structures (ports, seawalls, beach roads, and land reclamations by drainage) have been constructed. These have given rise to beach erosions. Then, coastal districts have become important scopes of human activities. Therefore, the erosions are very urgent and important problems.
　In this report, changes of shore lines in Japan are investigated by using aerial photographs taken in different years. Aerial photographs taken by U.S.-Force during 1946～1948 and those by Geographical Survey Institute, Ministry of Construction after 1961 are compared. Report Part 1 and Part 2 were published as No. 163 and No.192 of Technical Note of the Port and Harbour Research Institute.
　Very simple technique was used to analyze the photographs, that is, stable basic points were selected on photographs, and the ground distances between basic lines and points on the shore lines were measured. Shore line changes (erosion and accretion) are revealed as making zero the shore lines of photographs of U.S.-Force.