Rapid palatal expander which comprises an actuator element (2) provided with a drive head (3) and with two stems (4) with opposite threads, as well as a first and a second main body (5, 6) provided with aligned female threads (7, 8) that are each engaged by a threaded stem (4) of the actuator element (2). Guide means (9) are provided for guiding the simultaneous movement of the main bodies (5, 6) along the longitudinal extension direction Y of the actuator element (2) following the rotation of the drive head (2). Such guide means (9) comprise: a first and a second pair of rods (11, 12), which are fixed in a single body with the first and the second main body (5, 6), respectively, and are slidably mutually engaged with each other in a form relationship in order to guide the movement of the two main bodies (5, 6) with a single degree of freedom in the aforesaid longitudinal direction (Y).
