To provide a connection cylinder lock making a picking difficult by linking two or more of cylinder locks, and facilitating locking and unlocking.

This connection cylinder lock 10 has mutually linking two or more of cylinder units 12A and 12B. In the cylinder units 12A and 12B, an outer cylinder 13 is fixed to a cylinder case 15, and an inner cylinder 14 is rotatably inserted into this outer cylinder 13. A lock mechanism for locking rotation of the inner cylinder 14 is built in the outer cylinder 13 and the inner cylinder 14. Linking gears 16 and 16 are fixed on the same axis of the inner cylinders 14 and 14, and are mutually connected so as to mutually transmit torque of the inner cylinders 14 and 14.