[Purpose] In this study, we aimed to determine the components of activities of daily living that decline easily during hospitalization. [Participants and Methods] We performed a prospective cohort study of 2,819 inpatients who were hospitalized and discharged. We prospectively evaluated the Barthel Index at admission and discharge, age, length of hospital stay, clinical department, and rehabilitation type. We divided the inpatients into two groups based on the Barthel Index score at admission and compared the items of the index at admission and discharge to analyze the characteristics of decline in activities of daily living. [Results] Forty-nine inpatients (2.0%) had declined in activities of daily living. There were no significant between-group differences in age, length of hospital stay, clinical department, or ratio of individual rehabilitation. However, transfer and toilet use remarkably decreased in the group with Barthel Index scores at admission <85, and bathing and ascending/descending remarkably decreased in the group with Barthel Index at admission ≥85. [Conclusion] The characteristics of decrease in each activity of daily living vary, and our results suggested the components that easily declined when inpatients were divided based on their performance of activities of daily living at admission.