5 from rotating within the idling range provided for operation of the input shaft 5 before the output shaft 6 and the input shaft 5 are engaged with each other as a result when rotation of the key cylinder 2 operated through the key from the outside is transmitted to the lock mechanism as a rotational drive force the rotational ranges of the input shaft 5 to the unlocked state and the locked state are prevented from being unbalanced therefore in the door lock device extents to which the key is rotated for locking and for unlocking are prevented from being different from each other without an assembly process of the door lock device to the door d being complicated in all the embodiments described above the end portion of the output shaft 6 may have for example a cross section having an approximate cross shape instead of the approximate straight line shape the shaft portion 5 b engaged with the output shaft 6 is then provided with a groove approximately cross shaped and dividing longitudinally the shaft portion 5 b into four by adding a groove orthogonal to the recessed groove 8 according to the present invention the engagement piece positioned in both the recessed groove and the notched grooves is partially pushed out from the notched grooves by the output shaft when the output shaft is engaged with the recessed groove therefore the input shaft and the output shaft can be coupled to each other by simply engaging by the insertion described above the output shaft.