Provided is an injector in which adhesion between a stator and a rotor of an ultrasonic motor can be released efficiently. An injector (1) which injects a chemical liquid includes: an ultrasonic motor unit (3) including an ultrasonic motor (31); a drive mechanism (4) to be driven by the ultrasonic motor unit (3) so as to feed the chemical liquid when the ultrasonic motor (31) rotates forwardly; and a control device (5) which controls the ultrasonic motor (31) of the ultrasonic motor unit (3). The ultrasonic motor (31) includes a stator (32) and a rotor (33), and the control device (5) controls the ultrasonic motor (31) to alternately repeat forward rotation and reverse rotation so that adhesion between the stator (32) and the rotor (33) is released.