The invention discloses a cutting machine for steel bars and relates to the technical field of construction. The cutting machine for the steel bars comprises a machine body (2), a material containing rack (7), a shearing mechanism and a motor, wherein the shearing mechanism comprises a cutting device (5), a cutting platform (4), a hammer block (3) and an inertia force wheel (1); an operation platform is arranged at the middle of the machine body (2); the cutting platform (4) is arranged on the operation platform; the hammer block (3) is arranged above the cutting platform (4); the upper part of the hammer block (3) is connected to the crank shaft of the inertia force wheel (1) on the side face of the machine body (2); a tendon hole (6) is longitudinally formed on the cutting platform; the cutting device (5) is laterally arranged on the cutting platform; and a blade and a return spring (10) are arranged on the cutting device (5). The cutting machine for the steel bars can be used for directly cutting the steel bars in different lengths, and has the advantages that the operation is simple, flexible and suitable, and the problem that the traditional cutting machine only can be used for cutting end-product steel bars and cannot be used for cutting short steel bars is solved.