The invention discloses a building waste steel cutting device. The building waste steel cutting device comprises a base, a supporting leg, a front clamping plate, a rear clamping plate, a cutting front table and a cutting rear table. Lifters are fixedly connected to the left side and the right side of the bottom end of the base. The rear ends of the lifters are fixedly connected with second motors. The other end of a rotation shaft is rotationally connected with a connecting rod. The rotation shaft is fixedly connected with a cutting blade. The rotation shaft is in shaft joint with a half wrapping shell. The rotation shaft penetrates the cutting blade and the half wrapping shell. A cooling sprayer is arranged on one side of a supporting column, and a water injection port is formed in the back face of the supporting column and connected with the cooling sprayer. According to the building waste steel cutting device, through adding of multiple fixing devices, waste steel is fixed more stably when being cut, and the problem that since waste steel is not fixed in place, cutting is not safe is solved; and through adding of the cooling sprayer and the water injection port, when the cutting blade works, the cutting blade is subjected to atomization and cooling, and the problem that due to too high temperature, the cutting blade is prone to damage is solved.