A valve device of a turbocharger includes: a valve seat disposed on an entrance of a fluid passage divided into at least two branches, and an opening/closing valve coupled to a rotary shaft rotatably disposed adjacent to the valve seat. The valve seat has a contact surface which is flat and a dividing section which extends across the entrance and divides the entrance into two entrance sections. The opening/closing valve closes the entrance of the fluid passage disposed in the valve seat. The bottom surface of the opening/closing valve is in surface contact with the contact surface of the valve seat. The central portion of the opening/closing valve corresponding to the dividing section is spaced apart from the dividing section at a predetermined distance.