To provide a lock structure of an opening/closing panel capable reducing thickness of the opening/closing panel not to compress an occupant compartment, and reducing burden of a user at the time of opening the panel without restraining a design layout and design of the opening/closing panel and a rear seat.

In this lock structure of an opening/closing structure, a back panel diving the occupant compartment and a loading space of an automobile, and an opening/closing panel capable of opening and closing an opening opened and formed to the back panel and communicating the occupant compartment with the loading space are engaged or detached by mating of a striker and the lock mechanism. The lock mechanism is attached to the opening edge of the back panel, and the striker mated with the lock mechanism is attached to the opening/closing mechanism. An unlock mechanism is attached to the back panel and the opening/closing panel for releasing the mating of the lock mechanism and the striker.