The present invention provides a hydrogenation method capable of converting cracked kerosene into the raw materials for petrochemical cracking having a high thermal decomposition yield by a hydrogenation reaction. The present invention is a petrochemical process for producing at least any of ethylene, propylene, butane, benzene or toluene by carrying out a thermal decomposition reaction at least using naphtha for the main raw material, wherein cracked kerosene produced from a thermal cracking furnace is hydrogenated using a Pd or Pt catalyst in a two-stage method consisting of a first stage (I), in which a hydrogenation reaction is carried out within the range of 50 to 180° C., and a second stage (II), in which a hydrogenation reaction is carried out within the range of 230 to 350° C., followed by re-supplying all or a portion of these hydrogenated hydrocarbons to a thermal cracking furnace.