To provide a cylinder lock excellent in serviceability, allowing the outside diameter of an outer cylinder to be reduced and the wall thickness of a cover to be increased to provide strong protection against destruction.

The cylinder lock either permits or disables the rotation of an outer cylinder having a fitting hole on its axis and an inner cylinder for fitting into the fitting hole, by forcing a group of pins to move into or out of the cylinders. The outer cylinder has a plurality of lines of spring clearance grooves cut in its outer peripheral surface and has circular pin holes cut radially in each spring clearance groove and reaching the fitting hole. The inner cylinder has a key insertion groove cut along its axis and has pin holes bored therein which can communicate with the pin holes in the outer cylinder when the inner cylinder is fitted into the fitting hole. The group of pins consisting of bottom pins and drivers is inserted into the pin holes in the inner cylinder and the outer cylinder, and the cylinder lock has a plate spring enabling the outer end face of each driver to be elastically pressed, the plate spring using as its fixing point a base part secured to each spring clearance groove and using as its point of application the end of each of a plurality of branch parts provided to protrude from the base part. The plate spring is covered with a surface cover via fasteners which non-rotatably fasten the plate spring to the outer peripheral surface of the outer cylinder.