The invention discloses an equal-stroke double-vibrating device of an asphalt spreading machine, which comprises an eccentric shaft and a front vibrating device, a rear vibrating device, a left fixed supporting part and a right fixed supporting part which are installed on the eccentric shaft, wherein the eccentric shaft comprises a left outside eccentric segment, a left non-eccentric segment, a left inside eccentric segment, a central non-eccentric segment, a right inside eccentric segment, a first right non-eccentric segment and a right outside eccentric segment which are sequentially arranged from left to right and are connected with each other, the eccentric directions of the left outside eccentric segment and the right outside eccentric segment are identical, the eccentric distances of the left outside eccentric segment and the right outside eccentric segment are e1, the eccentric directions of the left inside eccentric segment and the right inside eccentric segment are identical, the eccentric distances of the left inside eccentric segment and the right inside eccentric segment are e2, e1 is equal to e2, the eccentric directions of the left outside eccentric segment and the left inside eccentric segment are opposite, and the eccentric directions of the right outside eccentric segment and the right inside eccentric segment are opposite. According to the invention, the influence of inertia force on the spreading machine is effectively eliminated, the structure of the vibrating device of the spreading machine is simplified, and the vibration influence of the vibrating device on an ironing plate during working is reduced.