A door latch device in a door of a motor vehicle, comprising: an engagement unit having an engagement mechanism adapted to engage with a striker of a vehicle body; and an actuator unit combined with the engagement unit and having an operation mechanism for operating the engagement mechanism, wherein the operation mechanism comprises; an inside lever carries out a release operation based on a door opening operation of an inside handle provided in the door inside the vehicle; a lock/unlock lever movable to an unlocking position and a locking position, based on an operation of a lock knob for locking and unlocking operations provided in the door inside the vehicle; an open link movable to the unlocking position and the locking position, interlocked with the lock/unlock lever, wherein, when in the unlocking position, enabling to release an engagement of the engagement mechanism and the striker based on a release operation of an outside handle provided in the door outside of the vehicle, and when in the locking position, disabling to release the engagement, a childproof lock mechanism having a childproof lever movable to a first position where is a childproof unlocking state that transferring the release operation of the inside lever to the engagement mechanism and enabling to release the engagement of the engagement mechanism with the striker, and a second position where is a childproof locking state that the transferring is disabled and disabling release operation from the engagement of the engagement mechanism with the striker, a double lock lever movable to a double unlocking position where allowing the movement of the open link into the locking position or to a double locking position where blocking the movement of the open link into the unlocking position; and a motor for moving the childproof lever to the first position, the second position, and a third position where passed through the second position, and movable the double lock lever to the double locking position by moving of the childproof lever to the third position, characterized in that, while the childproof lever and the double lock lever are supported on a common support shaft to form a coaxial, the childproof lever and the double lock lever are interlocked by an interlocking means (282a, 282b, 337) so as to move the double lock lever to the double locking position linked with the movement of the childproof lever to the third position. an engagement unit having an engagement mechanism adapted to engage with a striker of a vehicle body; and an actuator unit combined with the engagement unit and having an operation mechanism for operating the engagement mechanism, wherein the operation mechanism comprises; an inside lever carries out a release operation based on a door opening operation of an inside handle provided in the door inside the vehicle; a lock/unlock lever movable to an unlocking position and a locking position, based on an operation of a lock knob for locking and unlocking operations provided in the door inside the vehicle; an open link movable to the unlocking position and the locking position, interlocked with the lock/unlock lever, wherein, when in the unlocking position, enabling to release an engagement of the engagement mechanism and the striker based on a release operation of an outside handle provided in the door outside of the vehicle, and when in the locking position, disabling to release the engagement, a childproof lock mechanism having a childproof lever movable to a first position where is a childproof unlocking state that transferring the release operation of the inside lever to the engagement mechanism and enabling to release the engagement of the engagement mechanism with the striker, and a second position where is a childproof locking state that the transferring is disabled and disabling release operation from the engagement of the engagement mechanism with the striker, a double lock lever movable to a double unlocking position where allowing the movement of the open link into the locking position or to a double locking position where blocking the movement of the open link into the unlocking position; and a motor for moving the childproof lever to the first position, the second position, and a third position where passed through the second position, and movable the double lock lever to the double locking position by moving of the childproof lever to the third position, characterized in that, while the childproof lever and the double lock lever are supported on a common support shaft to form a coaxial, the childproof lever and the double lock lever are interlocked by an interlocking means (282a, 282b, 337) so as to move the double lock lever to the double locking position linked with the movement of the childproof lever to the third position.