The invention discloses a device and method for accurate positioning measurement of an ellipsometer. The device comprises a positioning piece, a sample table, an automatic two-dimensional mobile platform, a light intensity detector, a minipump, a microscope imaging system, a lighting source and a computer. A light spot outline can be clearly defined by utilizing a positioning hole in the positioning piece, the light intensity detector under the positioning hole is embedded in the center of the sample table, and can move accurately according to a step length together with the automatic two-dimensional mobile platform along an X-axis and a Y-axis, on the basis of using the microscope imaging system to observe and initially determining the position of the positioning hole, a light intensity value obtained by the light intensity detector is utilized to accurately adjust the position of the positioning hole so as to enable the light spot and the positioning hole to be completely superposed, then the catching frame of the microscope imaging system is moved onto the positioning hole, the catching frame represents the accurate position of the light spot, and the catching frame is positioned in a structure to be measured of a sample, thereby starting ellipsometry measurement. By the device and the method disclosed by the invention, the accurate positioning measurement specific to a concrete structure is realized, the operation is convenient, and the work efficiency is high.