The present invention provides a forced thin film-type flow reactor that, in addition to a pressure balance mechanism with which it is possible to set and adjust the clearance between processing surfaces using pressure balancing, is provided with a clearance adjustment mechanism that allows the clearance to be set and adjusted by an alternative means. The flow reactor processes a fluid for processing by passing the fluid for processing between a first processing surface and a second processing surface disposed so as to be capable of moving towards and away from each other, and the flow reactor comprises a pressure balancing mechanism and a mechanical clearance mechanism. The pressure balancing mechanism forms a minuscule first clearance by providing pressure balance between the pressure applied by the fluid for processing, which acts in the direction in which the first processing surface and the second processing surface move away from each other, and a force produced by a back pressure mechanism, which acts in the direction in which the first processing surface and the second processing surface move towards each other. The mechanical clearance mechanism mechanically sets a second clearance, which is greater than the first clearance, and makes it possible to set the clearance irrespective of the pressure of the fluid for processing.La présente invention concerne un réacteur à écoulement forcé à film mince muni, en plus d'un mécanisme d'équilibrage de pression permettant d'établir et de régler l'espace libre entre des surfaces de traitement à l'aide d'un équilibrage de pression, d'un mécanisme de réglage d'espace libre permettant d'établir et de régler l'espace libre à l'aide d'un moyen alternatif. Le réacteur à écoulement traite un fluide à traiter au moyen du passage du fluide à traiter entre une première surface de traitement et une seconde surface de traitement, disposées de façon à pouvoir se déplacer l'une vers l'autre et s'éloigner l'une de l'autre, et le réac
