Disclosed are height adjustment devices and folding tables. A height adjustment device includes movably coupled inner and outer sleeves. The inner and outer sleeves are coupled to first and second legs of a table. The height adjustment device also includes an elastic positioning pin and a cord. The elastic positioning pin is disposed on an external side of the outer sleeve to selectively engage with the inner sleeve. The cord is coupled to the elastic positioning pin and configured to pull the elastic positioning pin outward to disengage the elastic positioning pin from the inner and/or outer sleeves.