Railway operators adjust timetables, and reschedule rolling stock allocation and crew duties when train operations are disrupted due to accidents. This paper discusses the problem of rescheduling locomotive assignment to freight trains after timetable adjustment has been completed. The problem is modeled as an integer programming problem with set-partitioning constraints, and is solved by column generation technique. Numerical experiments using real data have revealed that our method provides a locomotive-rescheduling plan of satisfactory quality in acceptable computing time.