When we remember of our own childhood days, we will find that we have little memories about the time before 3 years old. This phenomenon was called 'childhood amnesia' by Freud (1905). In this article, some theories on childhood amnesia are reviewed. Then, we point out weak points on these theories, and indicate a new theoreticel idea based on Ohara (1994). The aim of this article is to show the fact that the occurance and the formation of autobiographical memory depend on the temporal organization of individual episodic memories. And finally we suggest that the childhood amnesia might well be explained from the obtained result that the period of the childhood amnesia is placed before the stage of temporal organization of episodic memories.