A method of calculating the natural frequencies of the axial vibrations of steam turbine blades and thick disks is presented, and the natural frequencies of blades are calculated and compared with the measured values. It is found that the difference between the calculated and measured values is within 10 per cent. The natural frequencies become higher at about 30 per cent depending on the defaults of the rotary inertia and the shear deformation. The effect of rotary inertia is small, while that of shear deformation is large. The relationship between the number of nodal diameters and natural frequencies is made clear by calculation.