The purpose of this study is to examine what variables influence on tweet credibility and attitude toward tweet. For this, the present research used the tweet content(information/opinion), tweet function(without URL and RT/URL/RT) and involvement(low/hight) as independent variables and applied a triangular research design which are in-depth interview, survey and computer usability testing software. Main findings are as follows. First, the participants read tweets listed in order regardless of tweet content, function and involvement. Second, there was a significant main effect of the tweet content on the tweet credibility and an interaction effect of those three independent variables on the attitude toward tweet. Finally, the in-depth interview showed that information is perceived to be more credible than opinion and URL>RT>just information or opinion are listed in order on the tweet credibility.