An optical isolation device comprising at least one optical isolation element, wherein the optical isolation element comprises a polarization conversion element and a polarizer, which are sequentially disposed, wherein the polarization conversion element is configured such that it can convert unpolarized light incident in a first direction into linearly polarized light and output the polarized light in a second direction, wherein the polarization conversion element comprises a polarization splitter for splitting the incident light into a vertical mode pair of polarized lights, and a retarder, wherein the polarization splitter is a polarizing beam splitter, a wire grid polarizer, a dual brightness enhancement film or a cholesteric liquid crystal film, wherein the polarization conversion element and the polarizer are located such that light incident on the side of the polarization conversion element can be transmitted through the polarization conversion element and then face to the polarizer, wherein the polarizer is an absorbing linear polarizer having a transmission axis formed in one direction and an absorption axis formed in a direction perpendicular to the transmission axis, where the transmission axis is formed in a direction parallel to the linearly polarized light, wherein a λ/4 plate is further comprised at a position where light transmitted through the polarizer along the first direction can enter, and wherein the λ/4 plate is disposed such that its slow axis can form any one angle in a range of 40 degrees to 50 degrees or any one angle in a range of 130 degrees to 140 degrees with the transmission axis of the polarizer. wherein the optical isolation element comprises a polarization conversion element and a polarizer, which are sequentially disposed, wherein the polarization conversion element is configured such that it can convert unpolarized light incident in a first direction into linearly polarized light and output the polarized light in a second direction, wherein the polarization conversion element comprises a polarization splitter for splitting the incident light into a vertical mode pair of polarized lights, and a retarder, wherein the polarization splitter is a polarizing beam splitter, a wire grid polarizer, a dual brightness enhancement film or a cholesteric liquid crystal film, wherein the polarization conversion element and the polarizer are located such that light incident on the side of the polarization conversion element can be transmitted through the polarization conversion element and then face to the polarizer, wherein the polarizer is an absorbing linear polarizer having a transmission axis formed in one direction and an absorption axis formed in a direction perpendicular to the transmission axis, where the transmission axis is formed in a direction parallel to the linearly polarized light, wherein a λ/4 plate is further comprised at a position where light transmitted through the polarizer along the first direction can enter, and wherein the λ/4 plate is disposed such that its slow axis can form any one angle in a range of 40 degrees to 50 degrees or any one angle in a range of 130 degrees to 140 degrees with the transmission axis of the polarizer.