Disclosed is method for preparing ripe persimmon directly on a persimmon tree, comprising the steps of preparing a sealing cover (S1) providing an ethylene generator for generating ethylene gas in the sealing cover (S2) receiving each persimmon, which is dangled on the tree, with the sealing cover in which the ethylene generator is provided (S3) aging the persimmons for a desired period of time in the sealing cover and thus forming the ripe persimmon (S4) and removing the sealing cover and then cleaning the ripe persimmons (S5). Therefore, the ripe persimmons having a good taste and freshness can be simply and efficiently manufactured.