A device for measuring a thrust load acting on a rotor of a hermetically sealed kneader includes displacement sensors (19) and a load-calculating member. The displacement sensors (19) are configured to measure relative displacement along the axial direction of an outer ring-fixing member (17), which is for fixing the outer ring (16) of one end of a bearing (6), or a casing (18) with respect to an inner ring-fixing member (20), which is for fixing the inner ring (13) of the one end of the bearing (6), or the rotor (5). The load-calculating unit calculates the thrust load acting on the rotor (5) by multiplying the relative displacement measured by the displacement sensors (19) by a conversion coefficient.