Professional Skepticism in one of the fundamental concepts in auditing standards and statements and its major focuses is on questioning mind for critical evaluation of audit evidence gathered during the audit process. In auditing literature and standards referred consequences of professional skepticism such as, avoid ignoring suspicious circumstances; abstain from the use of incorrect assumptions in the determination of audit procedures and evaluating the results, but it has not been tested which are determinants of professional skepticism. In this research, by means of other studies in the field of professional skepticism (such as Hurtt 2013), major determinants of professional skepticism, include search for knowledge, suspension in judgment, self-determination, questioning mind, interpersonal understanding, and self-confidence have been investigated. Also, relationship between attribute of skepticism and culture and behavior characteristics has been investigated in the next step. For factor of culture we used renewed Gray’ s theory (1988) by Lavinia Olimid (2005). Also, we used Fah’ s revised model (2009) based on Schwartz’ s study (2001) to explain motivational behavioral values. We used structural equation methods and factor analysis by means of Lisrel software ver. 8. 8. To test reliability, validity and descriptive statistics of research we used PASW sofware ver. 18. According to the achieved results, three factors include search for knowledge, self-confidence and interpersonal understanding are major determinants of auditor's professional skepticism. Also, results show direct impact of behavioral factors on professional skepticism and no effect of culture factor.