[Purpose] To evaluate various key functions related to obstacle crossing motions in hemiplegic people based on the paralysis degree. [Subjects and Methods] Thirty-seven patients with maintenance-stage hemiplegia who could independently ambulate outdoors were included. Subjects’ crossing movements were measured using obstacles with heights of 10%, 20%, and 30% of the trochanter length. The relationship among maximal crossing height and isometric knee extension muscle strength, one leg standing time, Trunk Impairment Scale score, disease duration, and subject age was examined, as was the target variable of maximum crossing height and the top four measurement items, to determine the explanatory variables. The participants were grouped based on Brunnstrom Recovery Stages III–IV (severe spasticity) and V–VI (mild spasticity). [Results] The explanatory variables were the Trunk Impairment Scale in the severe spasticity group and unaffected side-knee extension muscle strength in the mild spasticity group (contribution rates: 75.6% and 21.0%, respectively). [Conclusion] Trunk function in the severe spasticity group majorly contributed to crossing obstacles. Furthermore, knee extension muscle strength on the unaffected side in the mild spasticity group moderately contributed to crossing obstacles. Selecting and implementing a physical therapy routine that is aimed at improving function, depending on the severity of paralysis, is necessary.