A power conversion device (1A, 1B, 1C) comprising: a rectifier circuit arranged to rectify an alternating-current voltage supplied from an alternating-current power supply; a smoothing capacitor arranged to smooth a direct-current voltage that has been rectified by the rectifier circuit and includes a ripple voltage; a voltage detection unit arranged to detect the direct-current voltage rectified by the rectifier circuit; an allowable voltage storage unit arranged to store an allowable voltage upper limit value and an allowable voltage lower limit value of a direct-current voltage used when controlling an operation of a load that operates on a basis of the direct-current voltage smoothed by the smoothing capacitor; a margin calculation unit arranged to calculate an upper limit voltage difference that is a value obtained by subtracting a maximum value of the direct-current voltage detected by the voltage detection unit from the allowable voltage upper limit value stored in the allowable voltage storage unit, and a lower limit voltage difference that is a value obtained by subtracting the allowable voltage lower limit value stored in the allowable voltage storage unit from a minimum value of the direct-current voltage detected by the voltage detection unit, and to decide that one of the upper limit voltage difference and the lower limit voltage difference that has a smaller value is a direct-current voltage margin; a margin range storage unit arranged to store a plurality of margin ranges for stepwise limiting the operation of the load; a load limitation decision unit arranged to decide a limitation on the operation of the load depending on a margin range including the direct-current voltage margin decided by the margin calculation unit among the plurality of margin ranges stored in the margin range storage unit; a load control unit arranged to control the operation of the load depending on the limitation decided by the load limitation decision unit; and a primary current detection unit arranged to detect a primary current flowing from the alternating-current power supply to the rectifier circuit, wherein the allowable voltage storage unit is configured to store a set including the allowable voltage upper limit value and the allowable voltage lower limit value for each of a plurality of primary currents, and the margin calculation unit is configured to calculate the upper limit voltage difference and the lower limit voltage difference using the allowable voltage upper limit value and the allowable voltage lower limit value of a set corresponding to the primary current detected by the primary current detection unit among a plurality of sets of the allowable voltage upper limit value and the allowable voltage lower limit value stored in the allowable voltage storage unit. a rectifier circuit arranged to rectify an alternating-current voltage supplied from an alternating-current power supply; a smoothing capacitor arranged to smooth a direct-current voltage that has been rectified by the rectifier circuit and includes a ripple voltage; a voltage detection unit arranged to detect the direct-current voltage rectified by the rectifier circuit; an allowable voltage storage unit arranged to store an allowable voltage upper limit value and an allowable voltage lower limit value of a direct-current voltage used when controlling an operation of a load that operates on a basis of the direct-current voltage smoothed by the smoothing capacitor; a margin calculation unit arranged to calculate an upper limit voltage difference that is a value obtained by subtracting a maximum value of the direct-current voltage detected by the voltage detection unit from the allowable voltage upper limit value stored in the allowable voltage storage unit, and a lower limit voltage difference that is a value obtained by subtracting the allowable voltage lower limit value stored in the allowable voltage storage unit from a minimum value of the direct-current voltage detected by the voltage detection unit, and to decide that one of the upper limit voltage difference and the lower limit voltage difference that has a smaller value is a direct-current voltage margin; a margin range storage unit arranged to store a plurality of margin ranges for stepwise limiting the operation of the load; a load limitation decision unit arranged to decide a limitation on the operation of the load depending on a margin range including the direct-current voltage margin decided by the margin calculation unit among the plurality of margin ranges stored in the margin range storage unit; a load control unit arranged to control the operation of the load depending on the limitation decided by the load limitation decision unit; and a primary current detection unit arranged to detect a primary current flowing from the alternating-current power supply to the rectifier circuit, wherein the allowable voltage storage unit is configured to store a set including the allowable voltage upper limit value and the allowable voltage lower limit value for each of a plurality of primary currents, and the margin calculation unit is configured to calculate the upper limit voltage difference and the lower limit voltage difference using the allowable voltage upper limit value and the allowable voltage lower limit value of a set corresponding to the primary current detected by the primary current detection unit among a plurality of sets of the allowable voltage upper limit value and the allowable voltage lower limit value stored in the allowable voltage storage unit.