Aberration correction optical unit which corrects a wave front aberration generated by an optical system, comprising: a first phase modulation element which includes an optical axis and corrects a predetermined component of a wave front aberration of the optical system for a polarized component parallel to the optical axis among a light flux passing through the optical system, and a second phase modulation element which includes an optical axis and corrects the predetermined component of the wave front aberration for a polarized component parallel to the optical axis among the light flux passing through the optical system, characterized in that a variable waveplate is disposed between the first phase modulation element and the second phase modulation element, includes an optical axis and is switched to function as a half-wave plate or to function as a waveplate providing a phase difference equivalent to an integral multiple of a wavelength of the light flux for two linearly polarized lights orthogonal to each other according to a change of a voltage to be applied, wherein the variable waveplate is disposed so that the optical axis of the variable waveplate has a predetermined angle of 45° with respect to the optical axis of the first phase modulation element or the optical axis of the second phase modulation element, and the first phase modulation element and the second phase modulation element are disposed so that the optical axis of the first phase modulation element and the optical axis of the second phase modulation element are parallel or orthogonal to each other, and wherein each of the first phase modulation element, the second phase modulation element, and the variable waveplate is a liquid crystal element, and for each of the first phase modulation element, the second phase modulation element and the variable waveplate, the optical axis is parallel to an orientation direction of each liquid crystal molecule, and the variable waveplate is configured to be switched to the half-wave plate or to the waveplate by a control circuit adjusting a voltage applied to the variable waveplate. a first phase modulation element which includes an optical axis and corrects a predetermined component of a wave front aberration of the optical system for a polarized component parallel to the optical axis among a light flux passing through the optical system, and a second phase modulation element which includes an optical axis and corrects the predetermined component of the wave front aberration for a polarized component parallel to the optical axis among the light flux passing through the optical system, characterized in that a variable waveplate is disposed between the first phase modulation element and the second phase modulation element, includes an optical axis and is switched to function as a half-wave plate or to function as a waveplate providing a phase difference equivalent to an integral multiple of a wavelength of the light flux for two linearly polarized lights orthogonal to each other according to a change of a voltage to be applied, wherein the variable waveplate is disposed so that the optical axis of the variable waveplate has a predetermined angle of 45° with respect to the optical axis of the first phase modulation element or the optical axis of the second phase modulation element, and the first phase modulation element and the second phase modulation element are disposed so that the optical axis of the first phase modulation element and the optical axis of the second phase modulation element are parallel or orthogonal to each other, and wherein each of the first phase modulation element, the second phase modulation element, and the variable waveplate is a liquid crystal element, and for each of the first phase modulation element, the second phase modulation element and the variable waveplate, the optical axis is parallel to an orientation direction of each liquid crystal molecule, and the variable waveplate is configured to be switched to the half-wave plate or to the waveplate by a control circuit adjusting a voltage applied to the variable waveplate.