A pliers includes a first body with an engaging groove and a second body with an elongated slot pivotally connected with each other. The elongated slot includes a left and right positioning grooves and a protruding portion disposed therebetween. A tap button is pivotally connected to the second body. A supporting member is disposed between the second body and the tap button. 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.