A motor drive system wherein an LC circuit exists between an inverter and a motor is such that switching of semiconductor switching elements Su to Sw and Sx to Sz configuring the inverter is controlled by an on-signal formed of a first on-signal, a second on-signal, and an off-state period of a time the same as the first on-signal provided between the first on-signal and second on-signal, and by an off-signal formed of a first off-signal, a second off-signal, and an on-state period of a time the same as the first off-signal provided between the first off-signal and second off-signal, and surge voltage applied to an input terminal of the motor is suppressed by the time of the first on-signal and the time of the second off-signal being set to one-sixth of a resonance cycle specific to the LC circuit.