To provide a turnover prevention device firmly fixing a powered two-wheel vehicle.

The turnover prevention device 1 for the powered two-wheel vehicle comprises: a front wheel holding device 3; a handlebar holding device 4; and a pressing means 53. The front wheel holding device 3 is provided with: a lower side holding part 19 having a swingable rearward lock part 31 storing the lower part of the front wheel at one swinging end and capable of pressing the rear side lower part of the stored front wheel forwardly at the other swinging end; and a forward lock part 43 capable of storing the front part of the front wheel by being moved or swung forwardly. The handlebar holding device 4 has grip holding parts 60, 60 holding both grips of the handlebar. The pressing means 53 presses the grip holding parts 60, 60 to the front wheel direction.