The present invention related to an apparatus and a method for calculating basic electricity charges, being capable of periodically collecting electricity usage information for each household by using a smart meter provided in an aggregate building in which power reception equipment is installed, calculating the monthly or yearly maximum demand power for each household using the collected electricity usage information, and then, automatically calculating the basic electricity charges for each household with respect to the basic electricity charges of an entire aggregate building in consideration of the calculated maximum demand power for each household obtained and a ratio of ownership shares for each household based on the ownership shares for each resident household.