A shorting device for facilitating the grounding of a converter to which a plurality of sub modules is connected in series. The device includes: a moving rod (40) provided on a main frame (10) on which sub modules (S) are provided, and moving in the direction traversing the sub modules (S); and contactors (50) provided at the moving rod (40) to be electrically connected to each sub module outer casing (1) according to the movement of the moving rod (40). In addition, a connection means (C) electrically connects the contactor (50), the sub module outer casing (1), and another adjacent sub module outer casing (1) to enable simultaneous grounding thereof. This invention connects the sub module outer casings (1), which form the converter, through the operation of the shorting device to ground the sub modules (S).