To provide a pocket knife, opened and closed one-handed without pressing the end of a back metal and without touching a blade body and the back metal in the pocket knife constructed so that the back metal is rotatably fitted to the backside between a pair of side plates through a support shaft, and the base end of the blade body is collapsibly journaled to the tip part between both side plates through a support shaft, and the projected part at the end of the back metal and the backside recessed part of the end part of the blade bode are engaged with each other to lock the pocket knife.

A projection and a cam provided on the blade body and a projection and a cam provided on the back metal are respectively connected to each other. The cam is journaled to the outside of at least one of the side plates through the support shaft, and the cam is rotated around the axis clockwise or counterclockwise to open and close the blade body one-handed without touching the blade body or the back metal.