A vehicle tailgate locking device may include a latch assembly configured to engage or disengage a striker, wherein the latch assembly includes a housing, a latch member disposed in the housing and configured to engage or disengage the striker by rotation, a pawl member rotatably disposed in the housing to restrain or release the latch member, a driving device configured to rotate the pawl member to release restraint of the latch member, an engaging member configured to restrain the pawl member by engaging the pawl member when the pawl member rotates to a position releasing restraint of the latch member, and a releasing portion configured to press the engaging member to release the restraint of the pawl member when the latch member is rotated to a position releasing the engagement of the striker.