Door locking device for vehicle

A vehicle door lock device comprising:

• a door lock configured to switch a door of a vehicle between a lock state and an unlock state;
• an electronic key that transmits a response signal upon receipt of a response request signal;
• and
• an onboard device installed in the vehicle, wherein the onboard device transmits the response request signal out of the vehicle and drives the door lock upon receipt of the response signal, wherein
• the electronic key includes
• a threshold value setting unit that stores a first threshold value setting a periphery of a first region generated by the response request signal and having a strong electric field strength and a second threshold value setting a periphery of a second region around the first region and having a weaker electric field strength than the first region, and
• a response signal generation unit that outputs the response signal including position information indicating whether the electronic key is located in the first region, outside the first region and in the second region, or outside the second region based on an electric field strength detected by the electronic key and the first threshold value and the second threshold value, and
• the onboard device includes an onboard controller that, upon receipt of the response signal, switches the door to the unlock state if the electronic key is remaining in the first region for a first fixed time length or longer and switches the door to the lock state if the electronic key is remaining outside the second region for a second fixed time length or longer.