To provide a drive unit which enables the analysis of a speed ripple generated in a drive motor without preparing a measuring apparatus separately and enables the simplification of the work of performance adjustment and the improvement of work efficiency.

This drive unit is equipped with a speed data holding buffer 41 which samples and stores speed data of a motor 2 for a specified time, a speed ripple analyzing processor 51 which computes a speed ripple value based on the difference between the maximum and the minimum of the stored speed data, a data holder 42 which updates and holds the computed present value of the speed ripple and its maximum, a speed ripple present value data display 14 which indicates the present value of the speed ripple in real time, a speed ripple maximum data display 15 which indicates the maximum of the speed ripple value, and a specifying key 71 which clears the maximum of the held speed ripple value.