A disk drive device in which emergency unloading at the start of the engine is prevented, a head may have a prolonged life and improved reliability as an HDD is achieved. A disk drive device is driven or the movement of a magnetic head is allowed after an engine start in a vehicle is detected by an engine start detecting part, so that emergency unloading can be prevented at the start of the engine. In order to detect the engine start, voltage values on four power supply lines for a vehicle power supply device are monitored or the outputs of various sensors such as a tachometer, a vibration detection sensor, an engine sound detection sensor, a vehicle speed pulse, a gyro sensor and a parking brake are monitored. In another embodiment, the number of emergency unloading occurrence at the start of the engine is reduced, which allows the head to have a prolonged life, so that the disk drive device has improved reliability as an HDD. The voltage values on two power supply lines, first and second power supply lines for a vehicle power supply device are monitored. The magnetic head is allowed to move when the voltage values on the first and second power supply lines attain a prescribed value after a prescribed time period after the voltage value on the first power supply line attains prescribed value.