A power conversion device that comprises a power conversion unit for converting direct current into alternating current and that performs variable speed control of a synchronous motor (PM motor) in which a permanent magnet is used, comprising: a current detection circuit (CT) for detecting current flowing through the synchronous motor (PM motor); estimation means for estimating a magnetic pole position of the synchronous motor (PM motor) at a startup of the synchronous motor; characterized by a nonvolatile memory for storing magnetic pole position estimation data indicating a magnetic pole position at a stop of the synchronous motor (PM motor), wherein when power supply to the power conversion device is cut off, the magnetic pole position estimation data at a stop of the synchronous motor (PM motor) is stored in the nonvolatile memory; selection means for enabling a user to select either magnetic pole position estimation data stored in the nonvolatile memory or magnetic pole position estimation data obtained by the estimation means, and a control unit for driving the synchronous motor (PM motor) using the magnetic pole position estimation data selected by the user via the selection means; and an operation panel for setting an operation condition of the power conversion device , wherein the operation panel enables selection by a user of either driving the synchronous motor (PM motor) using the magnetic pole position estimation data stored in the nonvolatile memory, if the synchronous motor (PM motor) is provided with a mechanical brake; or driving the synchronous motor by estimating the magnetic pole position of the synchronous motor by the estimation means for estimating a magnetic pole position at a startup of the synchronous motor, if the synchronous motor (PM motor) rotates through inertia or by a load after a stop. a current detection circuit (CT) for detecting current flowing through the synchronous motor (PM motor); estimation means for estimating a magnetic pole position of the synchronous motor (PM motor) at a startup of the synchronous motor; characterized by a nonvolatile memory for storing magnetic pole position estimation data indicating a magnetic pole position at a stop of the synchronous motor (PM motor), wherein when power supply to the power conversion device is cut off, the magnetic pole position estimation data at a stop of the synchronous motor (PM motor) is stored in the nonvolatile memory; selection means for enabling a user to select either magnetic pole position estimation data stored in the nonvolatile memory or magnetic pole position estimation data obtained by the estimation means, and a control unit for driving the synchronous motor (PM motor) using the magnetic pole position estimation data selected by the user via the selection means; and an operation panel for setting an operation condition of the power conversion device , wherein the operation panel enables selection by a user of either driving the synchronous motor (PM motor) using the magnetic pole position estimation data stored in the nonvolatile memory, if the synchronous motor (PM motor) is provided with a mechanical brake; or driving the synchronous motor by estimating the magnetic pole position of the synchronous motor by the estimation means for estimating a magnetic pole position at a startup of the synchronous motor, if the synchronous motor (PM motor) rotates through inertia or by a load after a stop. driving the synchronous motor (PM motor) using the magnetic pole position estimation data stored in the nonvolatile memory, if the synchronous motor (PM motor) is provided with a mechanical brake; or driving the synchronous motor by estimating the magnetic pole position of the synchronous motor by the estimation means for estimating a magnetic pole position at a startup of the synchronous motor, if the synchronous motor (PM motor) rotates through inertia or by a load after a stop. <EOS>