English is an official language in the world. Therefore, English has been holding an important position and becoming an essential course of study in several countries. It is also a vital element of national power. As above, English is became a part of our life, so we must have critical view about English as a global language. I will look into the causes and effects of having english as a global language through merits and demerits. The world is becoming smaller. It means that the world have a deep stake and a big communication : government, economy, society, culture and so on. This interchange is based on language, so English is important as a global language. First, we can communicate a commercial transaction and a correspondence through the Internet. It means that get the highest state of efficiency with the minimum of labor. It also reduces a waste of time and gives every facility. Second, having a good ability of English specially enhances state economy. Not only a large enterprise but also small and medium enterprises can have trade relations freely with foreign firms. Human resources can make inroads into foreign market in several fields. These produce national interests and qualitative growth. Third, we can communicate society and culture of each country easily. We sometimes have prejudices and misunderstanding about different society and culture. However, we can overcome these obstacles through conversation. Addition, we can widen our mental vision by cultural exchange. On the other hand, English sometimes bring about side effects. First, English is only the second language in Korea because we have mother language. Therefore, if English becomes an official language, many people must learn English purposely. Moreover, English will become essential progress of study like Korea, then it causes competition. Second, mother language may disappear if English occupy a high importance. Recently, Korea have serious problems because of the younger generation. They well speak and write english but Korean’s vocabulary ability is very poor. Also, they even go wrong spelling. These problems can cause loss of each country’s characteristics and identities.  English has a lot of advantages to the globalization age. However, use of blind English causes loss our identity. As a result, we must assume a critical attitude toward English.