An object of the present invention is to provide an oral preparation for promoting synthesis of tissue collagen, an oral preparation for promoting healing of skin wounds or an oral preparation for preventing or improving skin wrinkles or sagging, which is safe and has an excellent effect. The present invention can provide an oral preparation for promoting synthesis of tissue collagen, an oral preparation for promoting healing of skin wounds or an oral preparation for preventing or improving skin wrinkles or sagging, which comprises hydroxyproline or a salt thereof as an active ingredient.