This study intends to predict prospective defects and establish the plan of Preventive Maintenance through research and analysis of defect occurrences and their repair costs in the public equipment of ‘H’ apartment house from 1998 to 2001. According to results of the analysis, more than 90% of defects and their repair costs for 4 years of the building have occurred in heating, hot water and water supply equipments. In case of specific classification in each equipment, more than 60% of defects were found at hot water pipes and heating pipes, and their repair costs covered more than 60% of the total defect costs. After two repairs by ‘Preventive Maintenance’ had been performed in the year 1998, total defects and defects of each equipment each yew have increased in number from 1999 to 2001. But total repair costs and repair costs of each equipment have not increased as time has gone by, because repair costs have relationship with the price of materials and labor, the part of defect and the scale of repair.