To provide a vehicle seat fitted with a back board capable of ocularly acknowledging the latched direction of an operating knob or its releasing direction to/from a table board, also acknowledging even with the touching sense by hand, and giving a high-grade sense totally as a table facility.

A receptacle seat 17 to mate with the boss part 11 of the operating knob 10 is provided on the back surface of a seat back, and the edge frame 20 of a put-in/takeout hole 23 to mate with the grip part 12 of the knob 10 is formed on the plate surface of the table board, in which projections 15a, 15b, 16a, 16b and grooves 17a and 17b capable of making engagement and being put out owing to a slide contact in association with the rotation of the knob 10 are provided in dislocation to serve proprietarily for set-off clicking of the knob 10 where the boss part 11 of the knob 10 and the plate surface of the receptacle seat 17 are confronting and also to serve proprietarily for latching clicking of the knob 10 where the grip part 12 of the knob 10 and the edge frame 20 of the hole are confronting.