An objective lens actuator that can accommodate higher density and speed is provided by improving frequency characteristics of an objective lens.The objective lens actuator includes an objective lens, a cylindrical lens holder that holds the objective lens, and a reinforcement part disposed in an opening opposite to the objective lens of the lens holder. The reinforcement part has a size that occupies one third to one half of the cylindrical wall of the lens holder from the end of an aperture along the optical axis. In this range, the high order resonance frequencies of the lens holder can be increased, and therefore, it is possible to obtain an objective lens actuator that can minimize the vibration amplitude at the high order resonance frequencies.