Abstract: In a stitch density adjusting device of a circular knitting machine for knitting stockings, panty hose, tights and so on, a needle cylinder is moved up and down for adjusting the density of the stitches being formed. In order to move the needle cylinder up and down, a knitting control unit having a knitting program set therein supplies a control signal to a reversible pulse motor which causes the needle cylinder to move through a movement transmission mechanism. The temperature rise in the knitting head due to friction is detected by sensor in the head and compared with a set value in a comparator which delivers a temperature difference signal to the knitting control unit. The control unit operates to compensate for the temperature rise by controlling the pulse motor.