The invention discloses an overbreak cutter for a hard rock shield tunneling machine. The overbreak cutter comprises a double-blade hob, a driving rod, a guide rail and an oil cylinder, wherein the double-blade hob is arranged at the front end of the driving rod; the rear end of the driving rod is connected with a piston rod of the oil cylinder; the driving rod can realize reciprocating motion along the guide rail under the driving of the oil cylinder; the guide rail is fixed on a cutter disk; a limiting pin is fixed in the guide rail; the limiting pin is located on the front side of the driving rod; a limiting slot is formed on the limiting pin; the limiting pin is blocked on the driving rod through the limiting slot; a limiting step is arranged on the front side wall at the lower end of the driving rod. The double-blade hob of the overbreak cutter has an integrated structure; the structure is simple; the mounting is convenient; the strength and the safety are high; when the shield tunneling machine normally tunnels, the overbreak cutter can retract into the excavation diameter under the driving of the oil cylinder, so that the blade abrasion can be avoided, the service life of the hob can be prolonged and the construction cost is lowered; besides, the limiting pin of the overbreak cutter can limit the rolling shift motion and can reduce the construction error.