A reclining device for a vehicle seat of the present disclosure includes a base plate provided with an assembling depression, a gear plate inserted into the assembling depression, a mobile flange transferring a torque to a seatback, and a power transmission module installed in a central portion of the gear plate to eccentrically rotate the mobile flange and to inhibit power transfer in an opposite direction. In particular, the reclining device further includes a stopper having a stop protrusion on the mobile flange and the stop protrusion is inserted into an arcuate stop hole formed on the base plate so as to efficiently realizes the stopper's function to limit the forward and backward rotation angle of the seatback to a predetermined range using fewer parts, thus reducing the weight and production cost of a reclining device.