Ijma is ranked as the third shariah evidence after the Qur'an and Sunnah in the science of Usul. Shafi was the first one who made Usul which had been known and used by the Islamic scholars, into a written document and who ascertained that Ijma was the third of the shariah evidences. Kalam is one of the sciences in which Ijma evidence is used. The scholars of Kalam used this evidence as far as the science of Usul made it possible. They always used it without changing any basics of religious beliefs and acceptances. That the aqidah of Ahl al-Sunnah has been supported with Ijma which is regarded as one of naqly evidences, played an important role in eliminating suspicions which were tried to be aroused in momins' mind. In this article, the function and importance of Ijma evidence, which is one of the primary sources of the science of Usul, in the science of Kalam and Aqidah of Ahl al-Sunnah has been studied.