Analysis is carried out on millimeter-wave (MMW) dosimetry in culture dishes used in experiments on MMW biological effects at the cellular level. Finite-difference time-domain (FDTD) technique is employed to compute the 6 mm MMW power density (PD) irradiated into cells in a typical culture dish and the MMW power absorption density (PAD) of cells, followed by the qualitative and quantitative analyses on the outcomes. Indicated in the results, distributions of MMW PD irradiated into cells and the PAD of cells are complicated with evident inhomogeneity so that MMW dosimetry varies a lot in different position whose influence on the experimental outcomes is not neglectable. Consequently, the precise determination of dosimetry is of great importance to be conducted in related experiments.