To provide a cylinder lock which is positively protected from reading a key ridge of a key corresponding thereto, and can employ a number of tumblers having the same length.

The cylinder lock consists of a holder 1 and a cylinder main body 10 rotatably arranged in the holder 1. The cylinder main body 10 is comprised of a plurality of tumblers 14 and a side bar 20. Each tumbler 14 has a notch 16 in a side edge thereof. The side bar 20 protrudes from the cylinder main body 10 before insertion of the key 45, to thereby disable the cylinder main body 10 from being rotated. On the other hand, upon insertion of the key 45, the side bar 20 sinks in the cylinder main body 10, to thereby enable the cylinder main body 10 to be rotated. According to the cylinder lock thus formed, the tumblers 14 are arranged in parallel with each other, and they are dividedly energized in two opposite directions orthogonal to an insertion direction of the key 45. Further, before insertion of the key 45, key holes 15 of at least the tumblers 14 energized in the same direction are aligned with the insertion direction of the key 45.