A booster circuit of a motor drive apparatus has at least two sub-booster circuits connected in series. Each sub-booster circuit includes a booster coil, a boosting switching element, a reducing switching element and an output capacitor, and outputs, by boosting an input voltage, a boosted output voltage. The booster circuit 20 outputs from its final stage sub-booster circuit a booster output voltage, a total boosting ratio of which is a product of sub-boosting ratios of the series-connected sub-booster circuits. Thus, the booster output voltage supplied to a motor drive circuit is prevented from falling even when high power output is required.