To prevent the function of a safe from being ignored by an error by forgetting to draw out a key after locking a cylinder lock of the safe.

The door 3 of the safe is provided with the cylinder lock 6. The cylinder lock 6 is provided with an inner cylinder 39 with a perforated keyhole, an outer cylinder 40 fitted therewith, a box 27 slidably incorporating a bolt 26, and a connecting rod 41 transmitting the rotation of the inner cylinder 39 to the bolt 26. The box 27 is provided with a first sensor 37 being turned on when the bolt 26 is retreated (unbolted). The outer cylinder 40 is provided with a second sensor 52 sensing the pushing-up of a tumbler pin. When the second sensor 52 is held turned-on for 5 seconds or so after the first sensor 37 is turned off, it is determined to forget to draw out the key 50 and an alarm is issued by a buzzer.