We offer an approach to the analysis of measurements performed by the laser beam analyzers. The proposed criterion for accuracy of the laser power distribution measuring apparatus can be used for assessing the potential ability of laser beam analyzers for high accuracy evaluation of linear dimensions. The criterion takes into account the quality of the optics and scanning system, detector performance, and the method of measurement. The test setup allows testing of errors in the full power assessment and diameter measurement. These errors are connected to real physical values and therefore can be used to compare the performance of arbitrary laser beam analyzers. The key point is that the process of measurement is considered totally in the spatial frequency domain. This allows us to put the method specifics of the measurement in comparable terms, extract some important features of the measurement crosses, and create a base for comparing instrument accuracy.