SEAT BACK LOCK DEVICE

PROBLEM TO BE SOLVED: To provide a seat back lock device capable of maintaining an excellent engagement state even when an axial direction of a metallic mushroom-shaped striker engaged with the slit of a resin coated metallic plate like member is inclined with respect to the plate-like member.SOLUTION: A seat back lock device 1 provided to maintain an erected state of a seat back 6a of a seat 6 for a vehicle, comprises a hook member 2 keeping a slit 3a in an engaging plate part 3 and a striker 4 of mushroom shape having a shaft part 4a and an umbrella part 4b. The striker 4 has one end fixed to the seat back 6a. The hook member 2 is freely turnably mounted to a vehicle body through the medium of a rotary shaft 8. A recess 3d is formed on a vehicle rear side in an opposite area 3f on the engaging plate part 3 opposed to the umbrella part 4b when the slit 3a is brought into the engagement state with the shaft part 4a through the turning.