Al-Ghazali's al-Munqidh min al-Dalâl has become the subject of study by many Muslim and Western scholars. Most research related to the theory of doubt compared with Descartes' method. However, there is no study on the truth of knowledge, even though this theme is al-Munqidh's main theme. This research aims to analyse the concept of the truth of al-Ghazali's knowledge in al-Munqidh. In detail, this study discusses four issues. That is the forms of truth, the sources and means of attaining truth. Also, al-Ghazali's criticism of truth seekers. The method analysis used is content analysis with al-Munqidh as the main reference. Results research shows that (1) there are two forms of truth for al-Ghazali: ontological and epistemological. (2) the source of truth comes from revelation and reason, (3) the means to reach the truth are the senses, reason and heart. (4) al-Ghazali criticized the four truth-seeking groups and stated that their methods contained weaknesses, namely they could not be verified, mixed with falsehoods or used ratios that were not optimal. The results of this study indicate that al-Ghazali's concept of the truth of knowledge differs from Descartes' concept and modern epistemology. Al-Ghazali acknowledged something not accommodated in modern philosophy, namely the revelation and the heart as a source and means of knowledge.