An alternating current motor driving system provided with a plurality of alternating current generators, a common distribution bus, a plurality of power conversion devices, a plurality of power conversion control circuits, and a plurality of alternating current motors. According to one embodiment, each of the power conversion control circuits generates a current instruction for the corresponding alternating current motor based on a corrected speed instruction obtained by correcting a speed instruction for the corresponding power conversion device according to a bus frequency detection output. According to another embodiment, each of the power conversion control circuits generates a speed instruction for the corresponding alternating current motor in the range equal to or lower than an upper limit speed adjustment output obtained by adjusting an upper limit of the speed instruction for the corresponding alternating current motor according to a bus frequency detection output. According to still another embodiment, each of the power conversion control circuits has a current instruction unit for generating a current instruction for the corresponding alternating current motor in the range equal to or lower than an upper limit current adjustment output obtained by adjusting an upper limit of the current instruction for the corresponding alternating current motor according to a bus frequency detection output. Each of the power conversion devices controls, in accordance with a load fluctuation of the common distribution bus, an effective power exchanged with the corresponding alternating current motor based on the current instruction from the corresponding power conversion control circuit, thereby controlling the bus frequency to be a predetermined value corresponding to the corrected speed instruction, a predetermined value regulated by the upper limit speed adjustment output, or a predetermined value regulated by the upper limit current adjustment output.