A confocal optical scanner comprising an optical filter (20, 30, 60, 70, 80), the optical filter (20, 30, 60, 70, 80) comprising: a disk-shaped body (21, 31, 83) including a first surface and a second surface opposite to the first surface, the first surface having a plurality of pinholes (21a, 31a, 83a); and a plurality of first microlenses (21c, 31c, 83c) on the second surface, central axes of the first microlenses being misaligned by equal to or less than 100 micrometer from central axes of the pinholes, respectively; the optical filter (20, 30, 60, 70, 80) being configured to reduce a numerical aperture of an illumination light input into the optical filter and to output the illumination light having the reduced numerical aperture, and to increase a numerical aperture of return light input from a specimen and to output the return light having the increased numerical aperture; and a motor connected to the body and configured to rotate the optical filter (20, 30, 60, 70, 80); wherein the confocal optical scanner further comprises a microlens disk, a plurality of second microlenses being regularly disposed on the microlens disk, the plurality of second microlenses are configured to divide the illumination light into a plurality of illumination light beamlets, each pinhole (21a, 31a) is disposed on a focal plane of the second microlens, each pinhole (21a, 31a) is configured to allow one illumination light beamlet of the illumination light beamlets, which has been passed through the second microlens, to pass through, each first microlens (21c, 31c) is configured to reduce a numerical aperture of the illumination light beamlet and to output the illumination light beamlet having the reduced numerical aperture; when a beam input from the surface facing the specimen has a numerical aperture represented by sin (θ), a radius of curvature of the first microlens (21c, 31c) is, depending on a refractive index n and a thickness t of the substrate of the pinhole disk with microlens, decided so that the beam input from the surface facing the specimen has a numerical aperture represented by sin (2θ) in a space where the beam exists after being output from the surface opposite to the surface facing the specimen. a disk-shaped body (21, 31, 83) including a first surface and a second surface opposite to the first surface, the first surface having a plurality of pinholes (21a, 31a, 83a); and a plurality of first microlenses (21c, 31c, 83c) on the second surface, central axes of the first microlenses being misaligned by equal to or less than 100 micrometer from central axes of the pinholes, respectively; the optical filter (20, 30, 60, 70, 80) being configured to reduce a numerical aperture of an illumination light input into the optical filter and to output the illumination light having the reduced numerical aperture, and to increase a numerical aperture of return light input from a specimen and to output the return light having the increased numerical aperture; and a motor connected to the body and configured to rotate the optical filter (20, 30, 60, 70, 80); wherein the confocal optical scanner further comprises a microlens disk, a plurality of second microlenses being regularly disposed on the microlens disk, the plurality of second microlenses are configured to divide the illumination light into a plurality of illumination light beamlets, each pinhole (21a, 31a) is disposed on a focal plane of the second microlens, each pinhole (21a, 31a) is configured to allow one illumination light beamlet of the illumination light beamlets, which has been passed through the second microlens, to pass through, each first microlens (21c, 31c) is configured to reduce a numerical aperture of the illumination light beamlet and to output the illumination light beamlet having the reduced numerical aperture; when a beam input from the surface facing the specimen has a numerical aperture represented by sin (θ), a radius of curvature of the first microlens (21c, 31c) is, depending on a refractive index n and a thickness t of the substrate of the pinhole disk with microlens, decided so that the beam input from the surface facing the specimen has a numerical aperture represented by sin (2θ) in a space where the beam exists after being output from the surface opposite to the surface facing the specimen.