The invention discloses a folding device of a combined balancing car. The folding device comprises a connecting mounting bracket, a boosting connecting piece and a two-wheel balancing car, each of left and right rear sides of the connecting mounting bracket is coupled with a power folding bar, each of the connecting shafts of the left and right power folding bars is provided with a linkage gear, two identical linkage gears are further arranged between the left and right linkage gears, one of the linkage gears is provided with folding power, and the folding power includes a motor and a reducer;the rear end of each of the power folding bars is coupled with a folding connecting strip, the boosting connecting piece is arranged in the two-wheel balancing car, each of the left and right sides of the front end of the boosting connecting piece is provided with a folding coupling piece, and rear ends of the left and right folding connecting strips are respectively coupled with the left and right folding coupling pieces; the folding device is folded automatically when power of the two-wheel balancing car is turned off; the folding device is unfolded automatically when the power of the two-wheel balancing car is turned on. The folding device has the advantages of scientific and reasonable combination, safe and flexible driving, simpleness in structure and better service for society.