To provide a tumbler type cylinder lock which prevents abrasion from being caused by a tumbler itself, and enables an key code converting operation to be accurately performed without the occurrence of a malfunction.

The tumbler type cylinder lock comprises: an external cylinder 1; an internal cylinder 2 rotatably inserted into the external cylinder 1; the plurality of tumblers 3 which are arranged in partition grooves 2a partitioned and formed at the internal cylinder 2; a plurality of pinions 4 engageable with the tumblers 3, respectively; and a side bar 6 which is arranged in a part of the internal cylinder 2 in such a manner as to correspond to each of the pinions 4, and pressed so as to be protruded in the direction of the external cylinder 1. The tumbler type cylinder lock changes an unlocking position of the tumbler 3 by changing a position to make the tumbler 3 engaged with the pinion 4. The tumbler type cylinder lock is equipped with a swing gear 7 which enables the tumbler 3 to be fixed in a position to avoid an unlocking operation region of the tumbler 3.