A partition plate, which is used for dividing a luggage compartment of a vehicle, comprises a locking device with which the partition plate is lockably fittable to a luggage floor when either surface of the partition plate is put on the luggage floor. The locking device includes a C-shaped lock spring which nips a projecting pin of the luggage floor to lock the partition plate to the luggage floor. The spring is enlarged in diameter by the pushing of a aliding member of the locking device.