Korea Superconducting Tokamak Advanced Research (KSTAR) is upgraded for its KSTAR 3rd campaign for new target mission to produce the D-shaped plasma with a target plasma current of 500kA and/or pulse length of 5s. New Plasma Facing Components (PFCs) are installed which leads to the increase of the surface area of the vessel by a factor of about 5. The vacuum conditioning such as the vessel baking has been performed in order to remove various kinds of impurities including H 2 O, carbon and oxygen for the plasma. The total outgassing rate in the KSTAR 1st campaign was measured as 1.5×10 −4 mbarℓs −1 which is increased by a factor of 3 (6.49×10 −4 mbarℓs −1 ) in the KSTAR 3rd campaign. Nevertheless, the outgassing rates per unit area have been decreased from 9.31×10 −5 mbarℓm −2 s −1 to 1.22×10 −5 mbarℓm −2 s −1 due to the upgrade of baking system and series of baking operation.