A pedestal and a floor system of a clean room using the pedestal are provided to reduce the time and cost required by controlling the step coverage of access floors supported to one pedestal easily and excluding the necessity of additional maintenance or readjustment works. A pedestal(110) contains: a base unit(120) composed of a base flange(121) fixed on a foundation floor tightly using bolts or adhesives and four base pipes(122,124,126,128) erected from the base flange; and a support unit(130) coupled to the top of the base unit to be adjustable in height and composed of four screw shafts(132,134,138) inserted to each base pipe of the base unit, nuts(142,144,146,148) coupled to each screw shaft and four support heads(152,154,156,158) coupled to the top of each screw shaft to support each corner of four access floors(160). The floor system of a clean room using the pedestal is formed by arranging the pedestals regularly and arranging the access floors continuously in all directions.