To provide a cylinder lock severely coping with the dishonest unlock using a flat tip screwdriver and capable of preventing the generation of die wear at a shoulder part of a lock groove.

A fixed main body 1 of this cylinder lock is formed of an outside member 2 and an inside member 10 having a high surface hardness. Guide projections 12 of the inside member 10 are fitted in assembling grooves 5 of the outside member 2 to form the lock grooves 13, with which the tip of a disk tumbler 22 is engaged freely to be removed, are formed between the adjacent guide projections 12 and 12.