The reason why an atomizer works is frequently explained by applying Bernoulli's theorem to the air jet which forms behind an air release pipe. As early as 1948, Tani pointed out that applying Bernoulli's theorem to the air jet of an atomizer was not correct. He described that the pressure should be the atmospheric pressure at anywhere in the air jet. He explained that the reason an atomizer works consists in the fact that the suction pipe is partly located in the air jet. He carried out brief experiments. In spite of the existence of Tani's theory and his brief experiments, the mistaken explanation, in which Bernoulli's theorem is applied to the air jet, appears in many publications today. In this study, air flow patterns were observed and pressure distribution was measured mainly by using a large-scale model whose shape is geometrically similar to that of a small prototype of the atomizer, under the condition of dynamic similarity. These experimental results reconfirmed Tani's theory about why an atomizer works.