An oscillation limiting mechanism (4) is integrally provided to an engine mount (3) (a vibration proof mount device) of a power plant (P) mounted on an automobile in a traverse mount fashion. Not only is a stopper metal member (40) in the shape of an inverted U letter disposed so as to cross over a mount body portion (30), but a stopper rubber (42) is formed so that it protrudes from the rear end of a casing of the mount body portion (30) toward the rear side of the vehicle body. Not only is a hollow portion (43) formed in the interior of the stopper rubber (42), but a metal core body (44) is also embedded in the stopper rubber (42) so as to be revolvable around an axis in the vehicle body traverse direction as if it were a link. With such a construction adopted, the stopper rubber (42) is shear-deformed in the vertical direction with comparative ease even in a state where it is brought into contact with the rear side leg portion (40c) of a stopper metal member (40) and thereby receives a compressive force in the vehicle body longitudinal direction, and a dynamic spring constant of the mount (3) in the vertical direction does not rise so much even if the stopper acts in rapid acceleration or the like; therefore, enabling increase in surrounding sound in acceleration to be suppressed with a simple structure less of cost up while oscillation of the power plant (P) is limited in a similar way to that of a torque rod.