A power conversion device includes: a current vector detecting unit (5) that generates a torque current detection value (Iqf) and an exciting current detection value from a current detection value between the power conversion device and the plurality of induction motors (8A, 8B, 8C, and 8D); a slip frequency calculating unit (3) that generates a slip frequency on the basis of a torque current command value (Iqp) and an exciting current command value (Idp); a speed estimating unit (4) that generates an estimation speed of the induction motor on the basis of a deviation between the torque current detection value (Iqf) and the torque current command value (Iqp); a connection failure detecting device (6) that detects a connection failure of the plurality of induction motors (8A, 8B, 8C, and 8D) on the basis of the exciting current detection value; and a voltage vector calculation unit (1) that generates a voltage command value on the basis of an inverter frequency generated on the basis of the slip frequency and the estimation speed such that the torque current detection value (Iqf) follows the torque current command value (Iqp), the torque current command value (Iqp), and the exciting current command value (Idp).