A flow meter detects a flow rate of a fluid. The flow meter includes a housing having a flow passage, through which the fluid can be guided from an inlet opening of the housing to an outlet opening of the housing, a measuring tube, which is inserted into the flow passage and constricts the flow cross section in one section of the flow passage, and a holding device, by which the measuring tube is retained on the housing. A respective flow straightener having at least one aperture through which the fluid can flow is arranged between the inlet opening and the measuring tube and/or between the measuring tube and the outlet opening. The flow straightener is configured as a separate component part, which is secured on the holding device by a form-locking or force-locking connection.