To provide a fire prevention device for electric vehicle battery packs preventing, when a fire breaks out, spreading of the fire by cutting off oxygen supply and, when the vehicle is operated and when the battery is charged, retaining the cooling performance of the battery.

This fire prevention device for electric vehicle battery packs includes: a battery pack housing 11 that covers the battery pack 10, has an air inlet 12 and an exhaust outlet 13 and can circulate the air in the interior thereof; a fire sensor that is provided inside the battery pack housing 11 and detects gas when a fire breaks out in the battery pack 10; dampers that are provided in the air inlet 12 and the exhaust outlet 13 respectively and selectively open or close the air inlet 12 and the exhaust outlet 13; and a control part that transmits an open signal or a close signal to the dampers according to the detection or non-detection of the gas of the fire sensor.