A hook member of a vehicle seat lock engages with a striker fixed to a vehicle body. An opening lever is pivotally secured to the first base plate to constitute the first subassembly. The hook member is pivotally secured to the second base plate to constitute the second subassembly. The first base plate is coupled to the second base plate. Between the first and second base plates, a sensing member is pivotally secured in parallel with the hook member to detect invasion of the striker in the hook member.
