A sliding table assembly includes a sliding seat unit slidably mounted to a base unit. Two auxiliary sliding seats are slidably mounted to the base unit and disposed on two sides of the sliding seat unit. A connection member is connected between the auxiliary sliding seats. Two roller sets are respectively mounted to the auxiliary sliding seats. Each roller set has rollers to roll on the base unit. A driving screw rod is coupled to the sliding seat unit and embraced by the auxiliary seats. When the sliding unit is moved by the driving screw rod, it pushes the auxiliary sliding seats to slide together therewith.