The paper is devoted to the problem of the non-proffesional art (e.g. outsider art, naive art). In the Czech culture its theoretical basis was for the first time described and analyzed by a Czech avant-garde painter and writer Josef Čapek in his famous essays Nejskromnější umění which was published in 1920. The study presents Čapek’s attitude to this sphere of art: according to his theory non-proffesional art is a specific medium which allows to show the reality in its immediacy, authenticity and completeness and this fact has a significant meaning in the context of the crisis of academic art stated by Čapek. The Czech author also points one of the important distinguishing features of the outsider and naive art: this kind of art does not have its own tradition and it exists beyond the artistic movements.