This paper presents the effects of thermoelectric module arrangement on the cooling performance of an air conditioner using thermoelectric module. A prototype of air cooling system, employing several thermoelectric modules, has been designed and built. The evaporative cooling technique is adopted for hot side of the module. The number of thermoelectric module in the system has been varied in the range of $2{sim}8$. The optimal operation conditions, such as input power to the thermoelectric module, fans and pump, have been determined for each arrangement of the system and the cooling performance has been compared under the optimal operation. It is found that both cooling capacity and COP are increased as the number of thermoelectric module increased. It is also found that cooling capacity can be improved by connecting the thermoelectric modules in series than in parallel, while the COP is little affected.