The characteristics of multi-junction solar cell under concentration were evaluated by SPlCE (Simulation Program with Integrated Circuit Emphasis). We developed the multi-unit model and analyzed the effect of the chromatic aberration and intensity distribution for the multi-junction cells. In the multi-unit model, the same numbers of units as grid numbers are installed for every electrode, and the units were connected to each other with the lateral resistances. In order to obtain the generation current from each diode, we measured intensity of concentrated light through the pinhole using single-junction solar cells consisted of InGaP, GaAs and Ge as detectors. By using the multi-unit model, we could successfully calculate the electrical cell performances taking the chromatic aberration and intensity distribution into account, and the calculated value agreed well with the experimental value. The multi-unit model will be very useful for cell designs and performance analysis of the concentrator cells.