Disclosed are a method of producing fine particulate alkali metal niobate in a liquid phase system, wherein the size and shape of particles of the fine particulate alkali metal niobate can be controlled; and fine particulate alkali metal niobate having a controlled shape and size. Specifically disclosed are a method of producing particulate sodium-potassium niobate represented by the formula (1): NaxK(1-x)NbO3 (1), the method including four specific steps, wherein a high-concentration alkaline solution containing Na+ ion and K+ ion is used as an alkaline solution; and particulate sodium-potassium niobate having a controlled shape and size.