A reciprocating wrench for quick combining fastener includes a main body, a claw, and an elastic positioning device therebetween. The main body includes a concavely-shaped first jaw opening, which has a pivot end at an end thereof. The claw includes a concavely-shaped second jaw opening, which has a pivotal combination portion at an end thereof. The pivotal combination portion is pivotally connected with the pivot end, such that the claw and the main body pivotally move with respect to each other. The elastic positioning device allows the claw to optionally rotate toward a closing direction or remain in the opening status. Therefore, the claw is able to remain in the opening status for combining the fastener.