The mainstream approaches to understand the characteristics of North Korean mathematics education focus on the comparative studies between South and North Korean mathematics curriculum and textbooks through literature analysis. These approaches make it possible to understand what is taught in mathematics class of North Korean school. But it is hard to find any information on how teachers teach mathematics and how students learn it. This study searches North Korean class environment, preparation for class, teaching and learning methods to understand mathematics class in North Korea as they really are. It is extremely difficult to make first-hand observations on North Korean class. Instead, this paper adopted interviews with teachers who have experience of teaching in North Korean school and now live in South Korea. By doing this, it is possible to get some understanding, although somewhat limited, the real aspects of North Korean mathematics class. As a result, there are distinct differences in the characteristics of North Korean mathematics class environment, preparation for class, teaching and learning methods, compared with South Korean.