Abstract Background On March 11th, 2011, the Great East Japan Earthquake hit the Tohoku area, and more than 15,000 people lost their lives by the tsunami and earthquake. People who survived natural disasters, terrors, or serious diseases reported long-time psychological distress such as PTSD (Post Traumatic Stress Syndrome) or depression. This study aims to elaborate on factors associated with PTSD post the Great East Japan Earthquake after four years. Methods Quantitative and qualitative analysis from a questionnaire survey conducted after four years of the earthquake in 2015. The questionnaires included participants' attributes, IES-R scale to evaluate PTSD, loss of their families by tsunami and earthquake, their own tsunami experience, many relocations after the earthquake, lost job after the earthquake. The open-ended question asked them to write about their challenges in their lives and others. Results We received 3465 responses. Among those who responded, the IES-R scale was significantly larger in women (n = 1397) (aOR=1.55, p = 0.001) than men (n = 1966). Higher in those with more their own tsunami experience (aOR=1.35, p = 0.014), in those with lost loved ones (aOR=2.1, p < 0.01), and in those with more economic difficulties (aOR=1.6, p < 0.001). In addition, those with less social connectedness (aOR=1.34, p = 0.017) and forced to live separately with family members after the earthquake(aOR=1.36, p = 0.014) were significantly higher in the scale. From a quality analysis, we observed much psychological distress from participants. Discussion and Conclusions In this study, more than half in the PTSD risk group reported that they had never cared for mental pain after the earth quake. We overlook PTSD frequently. However, long-range monitoring and care are necessary for those affected by a significant disaster. Key messages PTSD after disasters have been overlooked frequently. A long-range monitoring and care are necessary after a significant disaster.