The invention discloses a punching device of an oil level gauge. The punching device comprises a R-cut punch, a round hole punch, a material return plate, a cavity, a positioning device, a punch assembly and a press machine, and further comprises a guide member and an elastic limit member used for providing lower pressure for the guiding member, wherein the bottom end of the guide member is provided with an oil level rod guide slot, the oil level rod guide slot is gradually widened from top to bottom along the guide slot, and the two guide surfaces of the oil level rod guide slot are symmetrically distributed in the vertical direction of the oil level rod guide slot; the central line of the oil level rod guide slot in the vertical direction, the central line of R-cut punch in the vertical direction and the central line of the round hole punch in the vertical direction are located on a same plane, the cavity and the material return plate are provided with guide holes for enabling the guide member to pass through, and the bottom end of the R-cut punch and the bottom end of the round hole punch are higher than the bottom end of the guide member when the elastic limit member is in a natural state. The oil level gauge is symmetric and attractive in appearance, and the punching device of the oil level gauge can prolong the service life of the oil level gauge and the guide pipe of the oil level gauge.