Objective : The purposes of this study are to examine the correlations among work ability and sleep quality in bus driver and to find the factors affecting work ability. Methods : The participants were 120 inpatients with bus driver. The Work Ability Index(WAI) was used for measuring work ability and the Pittsburgh Sleep Quality Index (PSQI) was utilized to measure sleep quality. The relationships among the variables were examined with Pearson correlation coefficients. And the stepwise multiple regression analysis were performed to identify the predictive variables that explain changes of work ability. Results : As a result of analyzing correlation of variables affecting work ability, there was negative correlation in contact sleep quality(p<.001) and working hours(p<.001). Finally, Work ability was identified as a factor that explains 48.2% of change in sleep quality(p<.001) and working hours(p<.01). Conclusion : It was found that intimacy of bus driver was a major variable to affect work ability. The sleep quality and working hours should be considered as a way to improve the bus driver work ability.