Agaricus bisporus is a functional food and among the most widely cultivated mushrooms in the world. In this study, we analyzed the genetic diversity and population structure of 23 Korean and 42 foreign A. bisporus cultivars using SSR (Simple sequence repeat) markers. Genetic diversity of A. bisporus cultivars was as follows: number of alleles was approximately 13; observed and expected heterozygosity were approximately 0.59 and 0.74, respectively; and polymorphic information content value was about 0.71. A. bisporus cultivars were divided into three groups using distance-based analysis. Genetic diversity of Group 2, which consisted of cultivars from various countries, was high. In addition, model-based subpopulations were divided into two, and the genetic diversity of Pop2 (Population 2), which had many cultivars, was high. The results of this study could be used in a breeding program for A. bisporus, such as the development of new genetic resources and securing diversity.