The dispersion relation of the magnetostatic volume wave in a normally magnetized ferromagnetic slab placed between two metal plates is analyzed. When the normalized spacesA=D1/SandB=D2/S, whereD1andD2are the spaces between the slab and the metals andSis the slab thickness, are finite, the cutoff frequency &OHgr;cexists in the dominant mode and becomes {&OHgr;H[&OHgr;H+1/(A+B+1)]}1/2, where &OHgr;H=Hi/4&pgr;Ms,Hiis the internal magnetic field, and 4&pgr;Msis the saturation magnetization. This frequency &OHgr;cgives the lower limit of the frequency region in which the magnetostatic volume wave exists and varies withA+Bfrom &OHgr;Hto [&OHgr;H(&OHgr;H+1)]1/2. The experimental values on the change of &OHgr;cwithA+Bhave agreed well with the theoretical results.