A demountable bracket, for holding tablet-desks on seats; that consists of a main body (1) that holds the tablet-desk (T) and with a general “L” configuration that has arranged permanently on its horizontal wing (11) a first anchorage part (2) and on its vertical wing (12) a second anchorage part (3); with the particularity that both anchorage parts (2), (3) have respective strategic shapes and are strategically oriented to mount/demount this assembly on a horizontal tube (A1) and on a vertical tube (A2) of the frame (A) of the seat without auxiliary tools or complex handling.