We can find a lot of studies on energy-saving of housing, but there is few study on relation between city block and energy consumption. So, in this study, we analyzed energy consumption for air-conditioning and lighting of detached house and reduction of energy consumption for cooling by natural ventiration with changing city block parameter, such as residential density, road width, oriantation and existence of openspace. As a result, it was showed that by changing of city block, energy consumption of air-conditioning and lighting changed 6% at the maximum and we considered about the ideal city block for energy-saving.