Abstract: A vehicle seat comprises a main seat portion, a main backrest rotatably attached to the main seat portion, and a retractable sub vehicle seat. The sub vehicle seat has a recess formed on a rear side of the main backrest, a sub backrest rotatably attached to the main backrest, and a locking mechanism for holding the sub backrest on a retracted position or an upright position. The main backrest has a frame assembly rotatably attached to the main seat portion, a front cushion section attached to a front side of the frame assembly, and a rear cushion section attached to a rear side of the frame assembly. The rear cushion section is positioned in a bottom of the recess for supporting buttocks of a passenger who sits on the recess. The rear cushion section has a dent portion for supporting the buttocks and a bulged portion for supporting thighs of the passenger.