A motor driving device includes a control circuit board provided with a control circuit configured to output a control signal of a secondary voltage and a power circuit board provided with power circuitry to which a primary voltage higher than the secondary voltage is applied. The power circuit board includes a first substrate provided with a primary voltage component group to which only the primary voltage is applied, and a second substrate provided with a converter component group configured to convert the primary voltage into the secondary voltage and convert the secondary voltage into the primary voltage.