A valve gear device for internal combustion engines incorporates a stem connected to an intake and exhaust valve which opens or closes an intake bore or exhaust bore opening in a combustion chamber of an internal combustion engine; a first spring which urges the stem toward the direction of blocking the intake and exhaust valve; a cam supported around a cam shaft; and a valve deactivating mechanism provided between the cam and the stem. The valve deactivating mechanism includes a first movable member which is movable toward the axial direction of the intake and exhaust valve in the bore formed in a cylinder head of the internal combustion engine; a relative movement regulating device which moves so as to cross the axis center of the stem so that the first movable member and the stem are released and engaged and which regulates or allows the relative movement between the first movable member and the stem; an oil pressure supplying and exhausting device which supplies and exhausts the oil pressure to the relative movement regulating device so that the relative movement regulating device moves; a valve which prevents the oil pressure from being supplied to the relative movement direction between the first movable member and the stem is dead center of one of the switching ones. When the relative movement regulating device is able to be engaged, the oil pressure supplying and exhausting means is activated.