To realize a constant focus control by constituting an optical disk device with a biaxial lens translation driving mechanism positioning an objective lens in the direction of an optical axis and a radial direction and a translation coarse adjusting mechanism moving the whole area of the recording range of the optical disk while mounting the objective lens to suppress a revolving combined vibration between both mechanisms to be generated around an axis parallel with the tangential direction of the circumference of an optical disk.

When a distance in a direction vertical to the surface of an optical disk 40 between the position of the point of action of the driving force fp of a translation coarse adjusting mechanism 43, a distance in the vertical direction between the centorid (g) of a boaxial lens translation driving mechanism 42 and the centroid G of the translation coarse adjusting mechanism 43, the primary resonance frequency of the supporting system of the mechanism 43, the gain cross angular frequency of the control system of the mechanism 43, the time constant ratio between phase compensation circuits of the control system of the mechanism 43 and the ratio of the mass of the mechanism 42 to the mass of the mechanism 43 are respectively defined as hp, ha, ωp1, ωp0, γp and μ, the ratio of hp to ha is set based on a value to be calculated from an equation.