To provide a rotary cutter driving device where power supply facility capacity does not increase, regenerative power is not consumed as heat, and contents of high frequency components do not increase.

This rotary cutter driving device comprises a two-way PWM convertor 15 that converts supply power to direct power supply boosted in voltage more than full wave rectification voltage of three-phase alternating power supply 29, and supplies the power to a vector control inverter 13 for outputting drive power of a rotary cutter 16 via a DC bus. The rotary cutter driving device also comprises a capacitor bank 14 that is connected to the output of the two-way PWM convertor 15 and can accumulate regenerative energy upon deceleration of the rotary cutter 16 so as to employ the accumulated energy as powering energy upon acceleration of the rotary cutter 16.