To provide a method for manufacturing a liquid injection head that is excellent in piezoelectric properties and maintains preferable injection properties for a long period of time, and to provide a method for aging a piezoelectric element.

The method for manufacturing a liquid injection head includes: a piezoelectric element forming process including the processes of forming a first electrode having a nickel acid lanthanum layer, forming a piezoelectric body layer above the nickel acid lanthanum layer, and forming a second electrode above the piezoelectric body layer; and an aging process of applying a voltage of 60-70% of the maximum drive voltage difference to be applied to the piezoelectric element, to the piezoelectric element.