A safety device for motor vehicle includes a flexible hollow annular body including an arched upper base portion, an arched lower base portion and two opposing connection portions connected between the upper and lower base portions at two opposite sides, a flexible arched upper push piece having one end thereof connected to the upper base portion and an opposite end thereof extending toward the lower base portion so that a first elastic space is defined between the body and the upper push piece, and a flexible arched lower push piece having one end thereof connected to the lower base portion and an opposite end thereof extending toward the upper base portion so that a second elastic space is defined between the body and the lower push piece.