Disclosed herein is a vehicular seat back table apparatus including: a guide member installed at each of both sides of a table installation space of a backrest and including a rack gear portion; a driving shaft at which a pinion rotatably, which is installed at a guide frame and engaged with the rack gear portion of the guide member, is installed; a driving unit rotated by a rotation varying unit connected to the driving shaft, installed at a side surface of a table, and including a rotating hinge shaft member configured to provide a rotational force to rotate the table when the pinion is moved along the rack gear portion; and an elastic bias portion configured to support the guide frame to move upwardly along the guide member.