A microscope apparatus comprising: a first light source which outputs linear polarization having a first wavelength; a polarization conversion element which comprises a liquid crystal layer containing liquid crystal molecules, and which converts the linear polarization to radial polarization by transmitting the linear polarization through the liquid crystal layer; an objective lens which focuses the radial polarization onto an object surface; a condenser lens which collimates light from the object surface; a light receiving element which receives the light collimated by the condenser lens; and a controller which applies an electric voltage depending on the first wavelength to the liquid crystal layer of the polarization conversion element; wherein the polarization conversion element is disposed on the light source side of the objective lens, and comprises a phase reversal element which reverses the phase of a part of incident light and a polarization plane rotation element which converts the linear polarization to radial polarization, arranged along an optical axis; wherein the polarization plane rotation element comprises the liquid crystal layer and two first transparent electrodes (31, 32) disposed in opposition to each other so as to sandwich the liquid crystal layer; wherein the liquid crystal layer has a plurality of regions (30a to 30h) disposed along circumferential direction with a first intersection point (C 1) of the polarization plane rotation element and the optical axis as the center, alignment direction of the liquid crystal molecules contained in each of the plurality of regions being different from each other; wherein each of the plurality of regions of the liquid crystal layer rotates, by an electric voltage depending on the first wavelength being applied between the two first transparent electrodes, the polarization plane of the component of the linear polarization passing the region in accordance with the alignment direction of the liquid crystal molecules contained in the region so as to become parallel to the radial direction with the first intersection point as the center; and wherein the phase reversal element has first annular portions and second annular portions alternately disposed along the radial direction with a second intersection point (C 0) of the phase reversal element and the optical axis as the center, and reverses the phase of the linear polarization or the radial polarization incident on the first annular portions relative to the phase of the linear polarization or the radial polarization incident on the second annular portions. a first light source which outputs linear polarization having a first wavelength; a polarization conversion element which comprises a liquid crystal layer containing liquid crystal molecules, and which converts the linear polarization to radial polarization by transmitting the linear polarization through the liquid crystal layer; an objective lens which focuses the radial polarization onto an object surface; a condenser lens which collimates light from the object surface; a light receiving element which receives the light collimated by the condenser lens; and a controller which applies an electric voltage depending on the first wavelength to the liquid crystal layer of the polarization conversion element; wherein the polarization conversion element is disposed on the light source side of the objective lens, and comprises a phase reversal element which reverses the phase of a part of incident light and a polarization plane rotation element which converts the linear polarization to radial polarization, arranged along an optical axis; wherein the polarization plane rotation element comprises the liquid crystal layer and two first transparent electrodes (31, 32) disposed in opposition to each other so as to sandwich the liquid crystal layer; wherein the liquid crystal layer has a plurality of regions (30a to 30h) disposed along circumferential direction with a first intersection point (C 1) of the polarization plane rotation element and the optical axis as the center, alignment direction of the liquid crystal molecules contained in each of the plurality of regions being different from each other; wherein each of the plurality of regions of the liquid crystal layer rotates, by an electric voltage depending on the first wavelength being applied between the two first transparent electrodes, the polarization plane of the component of the linear polarization passing the region in accordance with the alignment direction of the liquid crystal molecules contained in the region so as to become parallel to the radial direction with the first intersection point as the center; and wherein the phase reversal element has first annular portions and second annular portions alternately disposed along the radial direction with a second intersection point (C 0) of the phase reversal element and the optical axis as the center, and reverses the phase of the linear polarization or the radial polarization incident on the first annular portions relative to the phase of the linear polarization or the radial polarization incident on the second annular portions.