The anomalous sound attenuation due to spin fluctuations near the magnetic phase transition temperatures in itinerant magnets and the rare earth metals is theoretically studied. By applying Tsuneto and Kadanoff and Falko's formulas, the attenuation coefficient is calculated. The calculated results explain the critical anomalies observed in magnetic metals such as Ni and Gd. By comparing the results with that for insulating magnets, the expression of the exchange striction is obtained. The effect of magnetic field on the critical attenuation is discussed.