Provided is a method of providing an advertisement in an indoor space using a system including a processor and a memory storing information about a content of each of advertisements including a first advertisement. The method includes: (a) calculating a base fee of the first advertisement from a content of the first advertisement stored in the memory based on a first criterion determined in advance based on a viewer's impression of each advertisement; (b) calculating an additional fee of the first advertisement from the content of the first advertisement based on a second criterion determined in advance to determine whether to be an advertisement improper to the system; (c) selecting an advertisement to be provided from among the plurality of advertisements based on a sum of the base fee calculated and the additional fee calculated; and (d) outputting an instruction to provide, to the indoor space, the advertisement selected.