Background and Aim: Since public health measures are the only way to control the spread of COVID-19, strict quarantine measures have done around the world. This condition will definitely not be without psychological effects. The aim of this study was to determine the factors affecting the stress caused by COVID-19 in the medical staff and the general population. Methods: This cross-sectional study was conducted by a researcher-made questionnaire on 326 people in Qazvin province, Iran in the spring of 2020. The questionnaire consisted of 40 questions, in 3 sections: demographic information, general and main questions related to COVID-19 stress. The questionnaire was made available to the study population in Qazvin through virtual networks. Results: Of the 326 participants (117 men and 209 women), 71 were medical staff members and 255 in the general population. The mean stress scores of the general population, the medical staff in the corona and noncorona department, were reported 28. 7± 8. 4, 30. 1± 9 and 27. 3± 7. 8, respectively, with no statistically significant difference among the groups (p=0. 374). In the medical staff, access to social response systems (p=0. 02), considerable weight change (p=0. 019) and reluctance to perform daily activities (p=0. 001) were among the factors that had a significant relation with stress score. For the general population, sex (p=0. 001), the presence of a high risk elderly person in the family (p=0. 001), having a fatal case due to COVID-19 in the family (p=0. 014), exacerbation of the underlying disease (p=0. 003), job closure (p=0. 007), etc had significant relations with stress score. Conclusion: According to the findings of the present study, the level of stress in the study population was mild, but the psychological effects of coronavirus epidemics are undeniable. Access to psychological counseling systems can be an effective way to improve a person's mental state in quarantine