Rapid palatal expander provided with a first and a second main body actuatable to be moved along a longitudinal slide direction by an actuator element, and connected to at least one first and one second thread-like support arm intended to interact with opposite portions of a dental arch. The support arms comprise a transversely projecting portion, which is engaged in a shape relationship within an enlarged portion of a shaped seat obtained in the two main bodies. The shaped seat is extended on the external surface with an insertion opening of size at least equal to the transversely projecting portion.