A polyphenol increasing agent for plant leaves, a polyphenol and amino acid increasing agent for plant leaves, a resin pellet, a plant leaf storage sheet, and a method for manufacturing a plant leaf storage sheet which can improve the storability of the plant leaves such as leafy vegetables and tea leaves are provided. A polyphenol increasing agent for plant leaves includes proanthocyanidins and trehalose. The polyphenol increasing agent for plant leaves preferably includes proanthocyanidins and trehalose at a weight ratio of 1:15 to 1:60. A plant leaf storage sheet includes the polyphenol increasing agent for plant leaves.
