The IMO noise code revised in 2012 is applied to newly built ships whose tonnage are equal or larger than 1600GT’s. Particularly for vessels of 10,000 GT’s or more, the noise regulation value of the living quarter became more severe than before. As a countermeasure to the noise code in the living quarter, it is recommended to separate accommodation area from funnel casing structure. However, as the result of the separation, natural frequencies of the superstructure is expected to decrease and possibly cause resonance with the excitation due to the engine or propeller excitation. Therefore, in the present research we aim to elucidate the vibration characteristics of a separated superstructure of a chemical tanker with L × B × D = abt.146 m × 24 m × 13 m. We have calculated principal natural frequencies and modes of the separated superstructure by using finite element vibration analysis for 3 types of models, as 1) superstructure (S.S.) only on the rigid foundation, 2) S.S. with the aft part of the ship including the engine room considering the effect of the elastic foundation, and 3) whole ship model considering the effect of hull girder vibration including the effect of added mass of outer sea water. Then the effect of shallow water and proximity related to added mass are investigated by using the whole ship FE model. Finally some structural modifications to increase the natural frequencies are investigated by using the numerical analysis, and the effects of reinforcement on the vibration characteristics have been discussed by comparing with those of the original structure.