A cutting device of a cord-embedded rubber sheet member, the cutting device comprising: a conveying mechanism in which a cord-embedded rubber sheet member is placed, the cord-embedded rubber sheet member comprising a number of cords embedded side by side in unvulcanized rubber; a blade receiving portion disposed in one surface side in a thickness direction of the rubber sheet member and crossing the rubber sheet member; and a cutting blade disposed in the other surface side in the thickness direction of the rubber sheet member and held by a holder rotating about an axial center extending in the thickness direction of the rubber sheet member whereby a cutting-edge advancement direction turns about the axial center, in a state in which the rubber sheet member is sandwiched in the thickness direction by the cutting blade and the blade receiving portion, the cutting blade moving toward an extension direction of the cords whereby the rubber sheet member is cut between the cords, and further comprising a turning restoring mechanism that constantly applies, to the cutting blade before cutting the rubber sheet member, a turning restoring force that restores the cutting-edge advancement direction to a preset moving direction, characterized in that the cutting device comprising a turning adjustment mechanism that reduces the turning restoring force applied to the cutting blade during cutting of the rubber sheet member to be smaller than the turning restoring force applied to the cutting blade before cutting the rubber sheet member, or blocks application of the turning restoring force with respect to the cutting blade during cutting of the rubber sheet member. a conveying mechanism in which a cord-embedded rubber sheet member is placed, the cord-embedded rubber sheet member comprising a number of cords embedded side by side in unvulcanized rubber; a blade receiving portion disposed in one surface side in a thickness direction of the rubber sheet member and crossing the rubber sheet member; and a cutting blade disposed in the other surface side in the thickness direction of the rubber sheet member and held by a holder rotating about an axial center extending in the thickness direction of the rubber sheet member whereby a cutting-edge advancement direction turns about the axial center, in a state in which the rubber sheet member is sandwiched in the thickness direction by the cutting blade and the blade receiving portion, the cutting blade moving toward an extension direction of the cords whereby the rubber sheet member is cut between the cords, and further comprising a turning restoring mechanism that constantly applies, to the cutting blade before cutting the rubber sheet member, a turning restoring force that restores the cutting-edge advancement direction to a preset moving direction, characterized in that the cutting device comprising a turning adjustment mechanism that reduces the turning restoring force applied to the cutting blade during cutting of the rubber sheet member to be smaller than the turning restoring force applied to the cutting blade before cutting the rubber sheet member, or blocks application of the turning restoring force with respect to the cutting blade during cutting of the rubber sheet member.