A stage device includes a stage having a copper main body and an electrostatic chuck, a cooling unit disposed below the stage, and a power supply mechanism for supplying power to an attraction electrode of the electrostatic chuck from a DC power supply disposed below the stage. The power supply mechanism includes a pair of terminals disposed at an outer peripheral portion of the stage while being spaced apart from each other, a first power supply line having a pair of metal rods spaced apart from each other while extending toward the stage and being connected to the DC power supply, a second power supply line having a pair of metal rods spaced apart from each other and connected to the terminals, and a connecting unit where the metal rods of the first power supply line and the metal rods of the second power supply line are connected.