In order to examine the process of improvement in the walking ability of trans-tibia amputees fitted with lower-limb prostheses, this study carried out tests of free walking and fast walking movements in a man with a TSB trans-tibia prosthesis. The tests included measurements of hip flexion in a sitting position, walking speed, step length, step rate, supporting time and swing time. The measurements were carried out every two weeks, for a total of six times. Furthermore, in order to examine the connection between the subject's walking ability and his training programs, investigative records of the subject's muscle strengthening and rehabilitation with walking were also examined. The results showed that there were continuous improvements of muscle strength in both legs as a result of muscle training and rehabilitation during 11 weeks. An obvious improvement of walking ability was observed two weeks after the start of walking as muscle strength increased, and the differences between the two legs evident at the initial stage slowly decreased. This bilateral difference showed a conspicuous improvement from about the seventh week, and perfectly normal walking was achieved from the 11th week. However, these results need to be interpreted with caution because this was a case study involving only one subject with a lower-limb prosthesis, and was not a case in which the socket of the artificial leg had considerable non-conformity.