Posttraumatic stress disorder (PTSD) is linked to abnormal amygdala activities. This study measured amygdala functional connectivity using DSM-5 criteria. There were 33 participants in the PTSD group and 33 participants in a trauma-exposed control (TEC) group, who did not have PTSD according to the PTSD checklist of the DSM-5 (PCL-5). Our findings are as follows: (1) In the PTSD group, the amygdala had increased positive connectivity with the medial prefrontal cortex (mPFC) and hippocampus, and decreased positive connectivity with the inferior mPFC and insula. The amygdala had increased negative connectivity with the orbital prefrontal cortex and decreased negative connectivity with the insula in comparison with TEC group. (2) PCL of all participants was correlated with the connectivity between the amygdala and the mPFC, hippocampus, and insula. These regions overlapped with those identified in the between-group comparisons. However, there was no association between PCL of the PTSD group and connectivity in these regions. Abnormal functional connectivity between the amygdala and mPFC subdivisions, hippocampus, and insula reveals their importance in PTSD pathogenesis.