Sentiment Analysis is an important type of text analysis that aims to support decision making by extracting & analyzing opinion text. Identifying positive & negative opinions & measuring how positively & negatively an entity is regarded. Sentiment analysis of social media data while the use of machine learning classifier for predicting the sentiment orientation provides a useful tool for the users to monitor brand or product sentiment. As more & more user express their views & opinion on twitter. So twitter becomes valuable sources of people's opinions. Tweets data can be used to infer people's opinion about marketing & social studies that can spot general people's opinion in regard to the social event which is going to be in current on twitter. Using this can obtain greater accuracy and identify people's opinion.