This study was performed to investigate LBP(low-back pain) prevalence rate and its related factors inphysical therapists. A self-administered questionnaire survey was conducted to 522 physical therapists in Daegu and Gyeongsangbuk. The LBP prevalence rate for recent 6 months was $61.7\%$. According to age, the prevalence rate was highest in the group aged 24 or less for both male and female physical therapistis. For male physical therapists , it was higher in smokers and drivers, but for female ones, it was not in a significant relationship with smoking and driving. According to work experience, the prevalence rates of those who had been working for less than one year were the highest, and those who had been working at hospitals and clinics were $69.1\%$, significantly high. According to therapy techinque, the prevalence rate related ti PNF was $71.6\%$, the highest and to occupational therapy was $34.3\%$, the lowest. According to working environment for six months, in both male and female physical therapists. LBP prevalence rate was in a statistically significant relationship with work hours during the day, night and weekend duties, repetitive works, motions that bend or twist the waist, the number of patients per day, the number of time to help patients per day, the number of time to carry medical equipment per day and the length of time to work standing. The rate was also higher when physical therapists fekt nire stress from their work. According to the result of multiple logistic regression analysis, male was in a significant relationship with work experience and motions that bend or twist the waist and female was in a significant relationship with work hours during the night and weekend duties, the number of time to help patients per day, motions that bena or twist the waist, actions taken to protect the waist. As for the developmental pattem of LBP in the group of physical therapists with LBP for six moths, $15.7\%$ of them had LBP for first time, $42.3\%$ had recurred LBP, and $42.0\%$ had chronic LBP. As for the causes of LBP, $51.7\%$ said that it was because they worked in the same posture for a long time, and as for how to treat LBP, 48.8% said that they treated themselvs or got help from their co-wokers. The results presented above suggest that physical therapists are exposed to high risk of LBP caused form occupational activities. Therefire, it is necessary to improve working environment to reduce the occurrence of LBP and to develop education programs for preventing the occurrence and recurrence of LBP.