In order to measure two rotation errors on two axes with lower cost, a rotation error measurement method for coordinate measuring machine (CMM) or machine tool was proposed. The influence of additional mass fixed on the CMM carriage on rotation angle error was analyzed and verified. The interferometric highresolution angular displacement sensor was adopted to measure the two rotation angle errors of the CMM carriage at the same time, and the load on the CMM carriage was reduced by fixing only one plane mirror with a small mass on the carriage. In order to verify the correctness of this method, two rotation angle errors of two exemplary CMM were measured, and the results were compared with those measured by standard laser interferometer. The experimental results show that the maximum difference between the proposed method measured results and the measurement results obtained by using the standard interferometer is less than 4 μrad, which can meet the requirements of CMM angle error measurement with low cost.