The paper is devoted to the problem of the appropriateness of using the notion «public opinion» in connection with the Greek society and possibility of the ancient theater to affect on the public opinion. After examination of the notion «public opinion», the author concludes that the structuring elements of public opinion are a common source of information and a common field of communication. In that sense public opinion do not correspond with the Greek notion «opinion of the many». At the same time, the ancient polis had enough public spaces for communication and did not need special media to create a common information field due to the limited territory, and therefore there were all conditions in the ancient polis for the formation of public opinion. The crucial role in this formation was played by the theater, which was a powerful means of influence, along with poetry and music, forcing audience to think about important social and political issues.