An auxiliary function board of vehicle seats, comprising a device main body, wherein the device main body comprises a bottom plate and a supporting plate mounted on the bottom plate in a pull-out manner; the upper end of the supporting plate forms a horizontal placement surface, and the upper end of the bottom plate is provided with a boss on the side away from the supporting plate; a backing plate is mounted on the boss in an overturning manner; a pull-out plate is inserted from top to bottom on the backing plate; the pull-out plate is provided with a fixing device; the whole device main body is fixedly installed on the two metal rods on the seat back through the fixing device; at least two placing cavities of arbitrary shapes are formed on the bottom plate protruding from one end of the supporting plate.