For the left sliding door lock, the link unit that relays the handle movement from the vehicle passenger compartment is not properly press-molded, and therefore, it may not function smoothly, and a part of it may fail to go back in place when the door is opened from the vehicle passenger compartment. If this occurs, the door latch may remain unengaged, even when the door is closed, and in the worst case, the door might open while the vehicle is in motion.