This study conducted an in-depth analysis of the psychological states of teachers during the first outbreak of coronavirus disease 2019 (COVID-19) using data on school mental health projects related to COVID-19 in Daegu from May to June 2020. The participants comprised 811 (34.9%) male and 1,511 (65.1%) female teachers in 1,041 (44.8%) middle and 1,281 (55.2%) high schools. After schools reopened, the most common causes of unbearable stress were unusual experiences, fear of infection, and negative emotions. Moreover, 41.5%/40.4% reported experiencing anxiety/depression, out of which 25.1%/23.6%, 10.0%/14.0%, and 6.4%/2.8% exhibited mild, moderate, and severe levels, respectively. The study identified the following influencing factors of anxiety: being female (OR: 1.52), years of employment (≤5 and <15; OR: 1.36; reference: <5), average monthly household income (≤3,000,000 and <5,000,000 [OR: 0.69], 5,000,000 ≤ [OR: 0.67]; reference ≤1,000,000 and <3,000,000 won), depression (OR: 19.14), posttraumatic stress symptoms (OR: 11.65), job stress (OR: 9.13), resilience (OR: 0.37), and subjective well-being (OR: 0.45). We identified the following factors for depression: being female (OR: 1.51), aged 40s (OR: 1.70; reference: 20s), average monthly household income (≤3,000,000 and <5,000,000 [OR: 0.75], ≤5,000,000 [OR: 0.66]; reference: ≤1,000,000 and <3,000,000 won), anxiety (OR: 19.14), posttraumatic stress symptoms (OR: 4.03), job stress (OR: 14.04), resilience (OR: 0.29), and subjective well-being (OR: 0.33). The findings suggest a necessity for specific, systematic measures and psychological support to teachers vulnerable to the impact of disasters, such as the COVID-19 pandemic, to cope with disasters and improve school adaptation.