Owing to a trend of installing high-powerd engines for speed-up of ships, it becomes an important problem to clarify urgently the vibratory behavior of engine rooms of ships. In the first report¹⁾ the author theoretically analysed of the vibration of engine rooms in three dimensional state, and the computation of natural freqencies of them was considerably complicated as shown in the report. For the practical use it is desired to be more simple to predict them in the stage of initial design of ships. For this reason, the author tries to compute the natural frequencies of reasonably simplified structure of engine room, and to prepare the groupes of curves (Fig. 17, 18, 19) of natural frequencies vers. length of ship and dimensions of engine room, on the basis of the data and mean values of scantlings of the vibratory members in engine rooms of practical ships. The comparisons of the recently observed frequencies by many other shipbuilderse^6)_??_15) and estimated ones by using the prepared curves result in a fairly good agreement.