Organizations have long made good use of celebrities' images or preferences in order to transfer them to their brands. Typically, organizations and advertisers have done communication with customers in more friendly and smooth ways employing specific celebrities' awareness and popularity. Recently, domestic and foreign companies make their corporate and brand accounts to use them actively in the environment where consumers are evaluating new communication using SNS very positively and participating in it. This study aimed to investigate whether celebrities who exert their influence in Twitter as off-line can be used in marketing as an extension of the studies which diagnosed the advertising effect employing celebrity models, which have been conducted actively to date. Concretely, it aimed to examine what effect celebrities' Twitter advertising messages actually have on brand attitudes and brand credibility. The research findings indicate that the Twitter advertising messages of the celebrity advertising models have positive effects on the brand attitudes and brand credibility to some degree, and on the whole, when celebrity advertising models are used, bigger effects were exerted than message delivery using brand accounts. Concretely, if the advertising message is delivered using the celebrity advertising model account, brand attitudes of the ‘short sentence message’ and ‘photo’ types and brand credibility of ‘photo' type increased significantly. Therefore, it can be interpreted when an organization intends to post its advertising message in Twitter employing a celebrity advertising model, it will be more effective to use ‘short sentence’ message and ‘photo’ types in terms of brand attitudes, and 'photo' type in terms of credibility rather than 'link'. For the brand attitude, delivering advertising messages using the celebrity's account scored higher in 'short message' and link message' types compared to the case of using the brand account. Thus, it can be said that in Twitter delivering advertising messages using celebrities' accounts rather than brand accounts is more effective in brand attitudes. On the whole, in the case of brand credibility, there was no remarkable difference between before and after and there was no significant difference found between the celebrity account and the brand account, which indicates that brand credibility is not changed or generated easily by Twitter advertising message messengers or Twitter advertising message types.