A punch die comprising: a punch body comprising a punch edge portion at a lower end portion along an axis, a key projecting from an outer periphery, and a punch driver at an upper portion along the axis; a punch guide comprising an inner hollow elongated along the axis and receiving the punch body to be movable along the axis, and a keyway formed on an internal periphery of the inner hollow to extend along the axis and mesh with the key; a retainer collar rotatably combined with the punch guide at an upper end along the axis and around the axis, the punch driver passing through the retainer collar to be movable along the axis; a punch head screwed in an upper end portion along the axis of the punch driver to regulate a position of the punch driver; and an elastic member interposed between the punch head and the retainer collar to bias the punch driver upward along the axis, characterized in that: the punch guide comprises a peripheral slot formed on the internal periphery of the inner hollow so as to communicate with the keyway and elongated in a circumferential direction around the axis, and the retainer collar comprises a cylindrical portion fitting in the punch guide and an engaging projection portion formed on an outer periphery of the cylindrical portion and capable of passing through the keyway and engaging with the peripheral slot, and the retainer collar is so dimensioned as to have the engaging projection engaged with the peripheral slot in a state where the keyway is not aligned with the engaging projection portion in the circumferential direction, and is so dimensioned as to allow the engaging projection portion to pass through the keyway in a state where the keyway is aligned with the engaging projection portion in the circumferential direction. a punch body comprising a punch edge portion at a lower end portion along an axis, a key projecting from an outer periphery, and a punch driver at an upper portion along the axis; a punch guide comprising an inner hollow elongated along the axis and receiving the punch body to be movable along the axis, and a keyway formed on an internal periphery of the inner hollow to extend along the axis and mesh with the key; a retainer collar rotatably combined with the punch guide at an upper end along the axis and around the axis, the punch driver passing through the retainer collar to be movable along the axis; a punch head screwed in an upper end portion along the axis of the punch driver to regulate a position of the punch driver; and an elastic member interposed between the punch head and the retainer collar to bias the punch driver upward along the axis, characterized in that: the punch guide comprises a peripheral slot formed on the internal periphery of the inner hollow so as to communicate with the keyway and elongated in a circumferential direction around the axis, and the retainer collar comprises a cylindrical portion fitting in the punch guide and an engaging projection portion formed on an outer periphery of the cylindrical portion and capable of passing through the keyway and engaging with the peripheral slot, and the retainer collar is so dimensioned as to have the engaging projection engaged with the peripheral slot in a state where the keyway is not aligned with the engaging projection portion in the circumferential direction, and is so dimensioned as to allow the engaging projection portion to pass through the keyway in a state where the keyway is aligned with the engaging projection portion in the circumferential direction. the punch guide comprises a peripheral slot formed on the internal periphery of the inner hollow so as to communicate with the keyway and elongated in a circumferential direction around the axis, and the retainer collar comprises a cylindrical portion fitting in the punch guide and an engaging projection portion formed on an outer periphery of the cylindrical portion and capable of passing through the keyway and engaging with the peripheral slot, and the retainer collar is so dimensioned as to have the engaging projection engaged with the peripheral slot in a state where the keyway is not aligned with the engaging projection portion in the circumferential direction, and is so dimensioned as to allow the engaging projection portion to pass through the keyway in a state where the keyway is aligned with the engaging projection portion in the circumferential direction.