Abstract: A slitter knife holder has a rod for supporting a slitter knife. Strain gauges are attached to the rod. There is provided a conversion circuit for converting changes in electric resistance of the strain gauges due to the deflection of the rod caused by the pressure of contact of the upper blade with the lower blade of the slitter knife into a signal indicative of the pressure of contact of the upper blade with the lower blade. The signal from the conversion circuit may be applied to a contact pressure monitor for indicating the signal directly to an operator or to an automatic contact-pressure control system.