A steam turbine includes a turbine main body supplied with steam from a steam supply unit and a steam valve for controlling an amount of steam to be supplied from the steam supply unit to the turbine main body. The turbine main body includes a first connection unit; and pluralities of guide rods and threaded rods, each extending from the first connection unit. The steam valve includes a second connection unit configured to be coupled to the first connection unit; and a flange disposed around the second connection unit, to receive the guide rods and threaded rods through corresponding through-holes respectively formed in the flange. The first connection unit includes an inner circumference and an end surface provided around the inner circumference, and the guide rods and threaded rods are arranged symmetrically around the inner circumference of the first connection unit and are fixed to the first connection unit.