The status of English worldwide is prestigious as an international language. Furthermore, nowadays in Korea speaking English is regarded more modern and stylish than using the Korean Language. As a consequence, English mixing phenomenon is increasing in Korea, especially, in TV commercials. Along with this expanding proportion of English, English deviation that defers from the norm is common. Deviations in advertisements are sometimes made intentionally to make them more appealing and impressive to audiences. However, as Korean TV commercials are made by Korean non-native English speaker, we cannot just simply regard all advertisement texts that differ from the norm as deviation. Some of them are made unintentionally because of advertisers? carelessness or mistake, and they do not play any role in advertisements. It is important to differentiate whether they are deviation or error because it is related with constructing good brand image. Thus, in this paper I will try to classify advertisements that defer from the norm in Korean TV commercials into deviation and error based on their function and purpose within advertisements, and I will find out their types of deviation and error.