The invention relates to a pneumatic single-grain sowing machine, comprising: a closed housing (1)； a rotatably driven separating device (3), which has circularly arranged perforations (7A)； a fan, by means of which a pressure difference can be produced between the housing (1) and the interior of the separating device (3), the separating device (3) thus being designed to separate seed by means of the perforations (7A) with the aid of the pressure difference, the separating device (3) being designed as a closed hollow drum having two side walls arranged at a distance from each other. The aim of the invention is to create a separating device (3) that is designed to compensate slight housing expansions. This aim is achieved, according to the invention, in that a drive shaft (9, 9') is fed through at least one of said side walls, in that the hollow drum is sealed against the drive shaft (9, 9') by means of a sealing element, in that the hollow drum can be divided by a dividing plane, in that the hollow drum is formed by a rotary plate (6) and by a perforated disk (7) having the perforations (7A), that the dividing plane lies between the rotary plate (6) and the perforated disk (7) and is sealed by a seal (10) in the undivided state, and in that, after the interruption of the pressure difference, the separated seed is accelerated by the pressure difference in the dispensing line (8).
