To obtain a foliar spray agent comprising a fermented material composed of a trehalose-containing saccharide as a component and to provide a method capable of increasing yield of qualities (flavor) of rice and applying the foliar spray agent at the latter half of ripening period of rice plant.

This foliar spray agent comprises a fermented material composed of a trehalose-containing saccharide as a component and is either a vinegar obtained by subjecting a mixture of a trehalose-containing saccharide and a brewing alcohol to acetic acid fermentation or a vinegar obtained by carrying out alcohol fermentation and acetic acid fermentation by using a trehalose- containing saccharide.