A pliers includes a first body including an engaging groove, a second body, and a tap-button mechanism. The second body is pivoted with the first body, and the first body is pivotable relative to the second body. The tap-button mechanism includes two positioning grooves at the second body and a tap button pivoted on the second body. When the first body comes close to the second body, the tap button can be tapped to a first position and engaged in the engaging groove. Thus, the first body is blocked and cannot pivot relative to the second body. The tap button can be tapped to a second position and detached from the engaging groove. Thus, the first body is pivotable relative to the second body. A positioning block is extending from the tap button and can be engaged in any of the positioning grooves for positioning the tap button.