The invention relates to a single seed dispenser (10) for a precision automatic sower comprising a cover (11) for seeds to be distributed joined to a body (12) containing a cavity (24) in communication with an aspirator of the seeds via a conduit (22) inserted in a hole (23) realised on the body (12), a distribution disc (13) with holes (38, 54) contained in a compartment delimited by said body (12) and by said cover (11); a driving disc (31) joined through pins (53) to the distribution disc (13), both discs being put into rotation by means of a shaft (29) actuated by an actuator for commanding rotation of the discs (13, 31); and a selector device (14) for the seeds pivoted on the edge of the body (12), where the selector device (14) comprises a plate (142) which presents, on a side facing the centre of the distribution disc (13), at least two toothed portions (143, 144), having teeth of different sizes and a curved sector (59) mounted against the surface of the distribution disc (13) opposite to the plate (142) and is provided with protrusions (591) having inclined surface (592) facing the distribution disc (13) at holes (38) therein.