A liquid ejection device actuator unit is fitted to a nozzle unit including a liquid chamber of which an inside volume is variable by deformation of a liquid chamber side diaphragm and an ejection tube which ejects a liquid from the liquid chamber. The liquid ejection device actuator unit includes a movable plate (362) which comes into contact with the liquid chamber side diaphragm (364), a piezoelectric element (360) which comes into contact with the movable plate (362) at one end of the piezoelectric element in an expansion or contraction direction to deform the movable plate, and a support member (353) which is adhered to the piezoelectric element (360) at other end of the piezoelectric element in the expansion or contraction direction. At least one of a contact portion of the movable plate and the piezoelectric element and a contact portion of the piezoelectric element and the support member is adhered by a hard material containing adhesive (371) in which a hard material (372) with a larger elastic modulus than a hardened adhesive is mixed.
