This study aimed to examine sex and age-level differences in preschool children with respect to walking times on a course and on a balance beam with obstacles. Subjects were 324 healthy preschool children: 4-year-old boys (51) and girls (51), 5-year-old boys (50) and girls (60), and 6-year-old boys (62) and girls (50). A 5- or 10-cm-high obstacle (depth, 11.5 cm; width, 23.5 cm) was set at the halfway point of a course (length, 200 cm; width, 10 cm) that was drawn on the floor and a balance beam (length, 200 cm; width, 10 cm; height 30 cm). The children walked to the end of the course and on a balance beam, and returned as quickly as possible under three conditions: no obstacle, low obstacle, and high obstacle. In all obstacle conditions, children aged 4-4.5 years walked on the course and the balance beam significantly slower than children aged 5 and 6 years, and children aged 4.5-5 years walked more slowly than children aged 5.5-6 years and children aged 6 years. Both walking was significantly slower in children aged 5-5.5 years than children aged 6 years (course: aged 6.5-7 years) in the high-obstacle condition, and was lower in the high-obstacle condition than in the no-obstacle condition in children aged 4 years. No significant sex difference was found in children in either walking time in all obstacle conditions. The walking time on the course showed a significant curvilinear regression with age in boys except for the no- and low-obstacle conditions. All balance beam walking times showed a significant curvilinear regression with age in both sexes in all obstacle conditions. Finally, 4-year-old children walked more slowly than 5- and 6-year-old children on a course and on a balance beam regardless of the presence of the obstacles. Both walking abilities develop markedly in 4-year-old children, and children between 5.5 and 6 years walk at a similar speed. The two forms of walking, regardless of the presence of an obstacle, showed little difference based on sex in children aged 4-6 years. A 10-cm-high obstacle affects walking in 4-year-old children, but not in children older than 5 years.