A speed sensorless motor starting method that starts a motor by using an inverter, the inverter including: first and second arms (2u-P, 2v-P, 2w-P, 2u-N, 2v-N, 2w-P) each including a chopper cell (11-1, 11-2, 11-3, 11-4, 11-5, 11-6, 11-7, 11-8) that includes two semiconductor switches (SW1, SW2) connected in series and a DC capacitor connected to the two semiconductor switches (SW1, SW2) in parallel, each terminal of one of the two semiconductor switches (SW1, SW2) serving as an output terminal, the same numbers of chopper cells (11-1, 11-2, 11-3, 11-4, 11-5, 11-6, 11-7, 11-8) being cascade-connected in the first and second arms (2u-P, 2v-P, 2w-P, 2u-N, 2v-N, 2w-P) via the output terminals of the chopper cells (11-1, 11-2, 11-3, 11-4, 11-5, 11-6, 11-7, 11-8); and a three-terminal coupled reactor including a first terminal (a), a second terminal (b), and a third terminal (c) located on a winding wire between the first terminal (a) and the second terminal (b), the first arm being connected to the first terminal (a), the second arm being connected to the second terminal (b), and the motor to be driven being connected to the third terminal (c), and a DC power supply voltage being applied to each of the terminals of sides of the first and second arms (2u-P, 2v-P, 2w-P, 2u-N, 2v-N, 2w-P) to which the three-terminal coupled reactor is not connected, characterized in that the method comprises: a current command value creation step of creating a current command value (i u *) by using an amplitude command value (I 1 *) and a frequency command value (f*) increased from 0 to a prescribed value over a predetermined period of time; and a motor start control step of starting the motor by performing control so that a motor driving current output from the third terminal (c) can follow the current command value (i u *), wherein a feedback control of a primary current (i u, i v, i w) is carried out using an open loop control in which the amplitude command value (I 1 *) and the frequency command value (f*) of the primary current are given in the feedforward manner according to a load torque (T L). first and second arms (2u-P, 2v-P, 2w-P, 2u-N, 2v-N, 2w-P) each including a chopper cell (11-1, 11-2, 11-3, 11-4, 11-5, 11-6, 11-7, 11-8) that includes two semiconductor switches (SW1, SW2) connected in series and a DC capacitor connected to the two semiconductor switches (SW1, SW2) in parallel, each terminal of one of the two semiconductor switches (SW1, SW2) serving as an output terminal, the same numbers of chopper cells (11-1, 11-2, 11-3, 11-4, 11-5, 11-6, 11-7, 11-8) being cascade-connected in the first and second arms (2u-P, 2v-P, 2w-P, 2u-N, 2v-N, 2w-P) via the output terminals of the chopper cells (11-1, 11-2, 11-3, 11-4, 11-5, 11-6, 11-7, 11-8); and a three-terminal coupled reactor including a first terminal (a), a second terminal (b), and a third terminal (c) located on a winding wire between the first terminal (a) and the second terminal (b), the first arm being connected to the first terminal (a), the second arm being connected to the second terminal (b), and the motor to be driven being connected to the third terminal (c), and a DC power supply voltage being applied to each of the terminals of sides of the first and second arms (2u-P, 2v-P, 2w-P, 2u-N, 2v-N, 2w-P) to which the three-terminal coupled reactor is not connected, characterized in that the method comprises: a current command value creation step of creating a current command value (i u *) by using an amplitude command value (I 1 *) and a frequency command value (f*) increased from 0 to a prescribed value over a predetermined period of time; and a motor start control step of starting the motor by performing control so that a motor driving current output from the third terminal (c) can follow the current command value (i u *), wherein a feedback control of a primary current (i u, i v, i w) is carried out using an open loop control in which the amplitude command value (I 1 *) and the frequency command value (f*) of the primary current are given in the feedforward manner according to a load torque (T L). a current command value creation step of creating a current command value (i u *) by using an amplitude command value (I 1 *) and a frequency command value (f*) increased from 0 to a prescribed value over a predetermined period of time; and a motor start control step of starting the motor by performing control so that a motor driving current output from the third terminal (c) can follow the current command value (i u *), wherein a feedback control of a primary current (i u, i v, i w) is carried out using an open loop control in which the amplitude command value (I 1 *) and the frequency command value (f*) of the primary current are given in the feedforward manner according to a load torque (T L).